CHIPPENDALE IN THE CORRIDORS OF POWER. With the utmost in diplomacy, the State Department has persuaded private donors to part with $30 million worth of antique furnishings and transformed its sterile modern headquarters into something more stately.

Mrs. Christian Herter burst into tears the first time she saw the diplomatic reception rooms at the US State Department. The year was 1961, and her husband, the secretary of state, was giving a dinner at the State Department that night. ``It looked like a gangster's molls headquarters on the Twentieth Century-Fox lot,'' remembers curator Clement Conger. ``It was done in completely modern furniture, covered in purple, red, and turquoise, with red at the windows.''

Mr. Conger explains, ``Mrs. Herter, who was the Standard Oil heiress from New York, knew what was right and what was wrong. She said, `I've never been so mortified in my life as an American woman. This is what foreigners think of us. To think that this should happen in the State Department is unbelievable.' ''

Conger answered, `` `Mrs. Herter, it's not only unbelievable, it's right here. The dinner is at eight. It's now five. We can't do anything in three hours. But, if you like, I will volunteer to run a public campaign to furnish the rooms.'

``I had no idea I would be at it 24 years later,'' Conger continues. ``And I had no idea that for my sins at the State Department I would have to take on the White House [restoration] too. But that's life.'' Conger is curator of the State Department's diplomatic reception rooms and also White House curator.

Diplomacy without tears is the order of the day at the State Department, where a new $5.7 million ``Americana Project'' caps 24 years of refurnishing in appropriate style. The Americana Project involves the redecorating of the massive Benjamin Franklin state dining room for $3.6 million and the 10-room secretary's suite for $2.1 million.

The current secretary of state, George P. Shultz, sandwiched in some time between Nicaragua and Bonn recently to talk about the renovation, in which he has taken a deep interest.

Mr. Shultz sits in his favorite gold damask American Chippendale armchair, in front of the King of Prussia marble fireplace of his formal office, where the scent of a pine fire lingers in the air. He talks about how important the proper d'ecor is in terms of the atmosphere of diplomacy:

``I think it helps a great deal to have a setting that says something about our country. These rooms and the rooms upstairs say that we have a tradition that we're proud of, that our Founding Fathers were people of tremendous talent, and that the standards set for excellence of performance are high. So those are all good messages. . . .''

He adds that foreign visitors are particularly interested in the John Quincy Adams drawing room, with the desk that Thomas Jefferson himself designed and on which he drafted portions of the Declaration of Independence.

Secretary Shultz stands briefly for a photo in this large formal office, which would dwarf a smaller man. He is a tall and formidable figure, dressed all in blue, with royal blue eyes in a ruddy face.

An 1869 landscape of Mt. Chocorua in eastern New Hampshire, painted by Jasper Francis Cropsey, hangs over the fireplace. Above a serpentine-front Chippendale chest of drawers hangs a portrait of John Quincy Adams by Charles Byrd King (1785-1862). Paired Corinthian pilasters bearing the Great Seal of the United States are the chief architectural motif of the room, which is painted in what might be called antique banana. It is all quite grand, with its English cut-glass chandelier in the style of Robert Adam and its antique Heriz-Serapi rug.

The secretary of state admits he does most of his work, not here, but in the smaller, cherry-paneled ``back office'' just off this one, where he keeps pictures of his family. He prefers it for one-on-one chats with heads of state because it's more personal. The back office contains a Hepplewhite-style writing desk, two 18th-century Pembroke tables, and a Tabiz rug.

Initially, Clem Conger had planned to redo just the formal office, but Secretary Shultz, the former head of Bechtel Corporation, balked at that. ``I said, `Look, if we're going to do it, let's do it,' '' he recalls. `` `If you start to do one room, you disrupt everything. So if you're going to be disruptive, we might as well be disruptive and then do the whole thing, and not have a shabby thing and then something else.' So I was right about that. It's better to have gotten it all done.''

He chuckles, then says, ``One of the things I like about all this having been done while I'm here -- this and the Benjamin Franklin room and the Madison-Monroe rooms and the dining rooms done -- is it puts me in the position where I can say that nobody will be able to say that I never accomplished anything while I was secretary of state.'' He beams.

Secretary Shultz explains that an architect, Allan Greenburg of New Haven, Conn., was hired in 1984 to redesign the diplomatic reception rooms. Shultz worked closely with the architect and insisted that the job have a tight schedule, because they would have to be out of the offices for nearly seven months.

``The only time we could really do that was in the last half of an election year, because the amount of flow of people through here is a lot less than now,'' he explains. Local, expert craftsmen were hired, ``and we were interested in watching them work. The painting and the rubbing of woodwork in the next room were done with great care -- great, painstaking effort.

``We had some fun after it was completed,'' the secretary adds. The fun was a big party, delightfully devoid of protocol, which the secretary of state threw for the workmen and their families in the renovated rooms.

A tour of the secretary's suite of 10 classical rooms, like the earlier renovated diplomatic rooms on the floor above, is like a stroll through American history. The John Jay reception room, for instance, includes six Hepplewhite shield-back chairs said to have belonged to George Washington, and a pair of Hepplewhite inlaid card tables from the family of William Paca, a signer of the Declaration of Independence.

The George C. Marshall reception room includes a Chippendale sofa and American Chippendale armchairs and sidechair dating from 1770. The pale gold and burgundy Franklin dining room, redesigned by John Blatteau, is sometimes called the most expensive room in America. It is the length of an elegantly gilded football field, 100 by 47 feet. Thirty-three ounces of 24-karat gold gleam from the simulated French red marble columns done in Corinthian style, which stand like sentinels up and down the room, and from the Great Seal at the center of the ceiling. The total cost of this decorative gold and its application: $230,000. The $3.6 million face-lift transformed a modern steel, glass, and marble room into the sort of 18th-century state dining room Ben Franklin might have known.

When asked whether there's been any flap about a $5.7 million redecorating project at a time of government budget belt-tightening, Secretary Shultz answers:

``I didn't know it was that much, but, anyway, it's all private funds. There hasn't been any flap at all. I think people who come here -- members of Congress and people from around the country -- they're all delighted. They're thrilled with what has been done. I always kid Clem [Conger] and say he's one of the great con men of all time in getting people to give money and furniture and so on.

``But the fact is: It's a privilege to contribute to something like this. My wife and I contributed money, just because I think it's a good thing. Of course, if it had been taxpayers' money and funds, that would have been a different thing. But it was all contributed money.''

Does the secretary of state mind taking time out of the affairs of state to talk about diplomatic d'ecor, about Duncan Phyfe and Hepplewhite?

``Well,'' he says, ``it's all part of the affairs of state.

When Secretary Shultz kids about Clem Conger's being something of a con man, he's talking about Conger's rather alarming powers of persuasion. The curator is relentless as a Cossack in pursuing the antiques and portraits he covets for this 24-year renovation at the State Department. He will stalk a historic prey for years. During a nearly two-hour tour of the diplomatic reception rooms, Conger tosses off some stories about how he acquired this precious chest, that treasured painting for the collection.

He points with pride to a set of six Philadelphia Queen Anne chairs with balloon seats bought six years ago at auction for $100,000. ``I've since been offered $100,000 for just two of them.'' He smiles.

Then there is the $50,000 mahogany bomb'e chest he snared several years ago at another auction. It is one of only seven in the world, one of three in America, and the best of its kind. It would be worth between $750,000 to $1 million if sold today, says Conger.

He explains, ``I learned years ago when you see something wonderful you want for your collections, you have to grab it -- even if you don't have the money -- to keep it from getting away. Borrow the money. Make a down payment, because you'll never see it again, and, if you do, it'll be double, triple, quadruple that cost.''

The entire State Department collection is worth $30 million. Roughly one-third of it, valued at about $10 million, is on loan to the department. Clem Conger has an insidious way with loans. He stands in the dramatic John Quincy Adams state drawing room (72 feet long), with its mocha walls and yards of precious antiques, and tells about how he netted its namesake's portrait.

When the room opened in 1971, Conger called the John Quincy Adams descendant who owned the portrait and purred, ``Wouldn't you like to give the portrait of your most distinguished ancestor to the room named in his honor, because, although we have portraits of [him], he looks as though he's just eaten a quince? This one is so pleasing.'' The Adams descendant said, ``Oh, Mr. Conger, I couldn't give my ancestor away.'' Conger said he didn't blame him, but couldn't he loan it? And they would make a copy of it.

``My technique,'' says Conger, ``is that if we make a copy of something and it's any good, we offer it free to the owner of the original, if he will give us the original and take the tax deduction. It didn't work in the case of the Adams portrait. Not then. But 18 years later the Adams descendant died, leaving two portraits, both Mr. and Mrs. John Quincy Adams, to be divided among three children. They decided to give the portraits to the State Department to help pay the taxes on their father's estate, if Conger would give the copies to the eldest child. ``Which we did,'' he explains. ``That device has worked three times.''

Then there is the case of what Conger calls ``this grand Philadelphia marble-top table.'' It was in the entrance hall of friends of his for several years, and he constantly reminded them it was too large for the hall. ``They said, `Well, where else could we put our tennis rackets?' '' Conger insisted it was too good for tennis rackets. After four or five years of ``this banter,'' Conger says they called and offered to donate the antique to the State Department, if he'd replace it with a table of the right size. He sent over two tables so they could choose one to keep. ``They were English tables, very nice, but not so valuable as this table,'' he says proudly.

Then there was the bagging of the valuable Benjamin Franklin portrait in the vast, blue-green Jefferson diplomatic room. ``I called the president of the Franklin Mint,'' Conger explains, ``and said, `The finest portrait in the world of Mr. Franklin is on the market for only $200,000. You can't afford not to buy it, then make all the medals you want, and next year, 1976, give it to the State Department as a bicentennial gift.' It worked,'' says Conger.

Of course, many gifts have been donated, without Conger's nudging, by generous Americans. He tells the story of the collection's first important gift, a portrait of George and Martha Washington by Rembrandt Peale, given in 1961. ``It was the gift of a Hungarian immigrant, a man who came to America in 1950, made millions in machine tools, and gave the portrait to the State Department -- which he had never seen -- as his salute to freedom and appreciation for what this country had done for him. A great success story,'' murmers Conger.

Finally, he glances lovingly at John Hancock's Boston bomb'e secretary-bookcase, circa 1776, and says, ``This is one of the supreme examples of American craftsmanship. I assure you, every king, every queen, every prime minister, foreign minister, parliamentarian who comes to America and is entertained here simply cannot believe their eyes when they see wonderful things like this, because they thought that in the middle of the 18th century we were out in the wilderness fighting Indians. They didn't know we had transplanted culture.''