Top US planner sees 4 reasons for major expansion of economy

''If you look at the basics,'' says a high-ranking US government official, ''you see that the US economy contains the elements for sustained, noninflationary expansion.''

Steady growth without inflation? That is the prized goal that at least three presidents -- Ford, Carter, and now Reagan -- have striven to achieve, so far in vain.

This man, who holds a senior federal government post, ticked off reasons for his assessment:

* Real progress has been made against inflation.

* Labor costs are more moderate. The adversative relationship between management and labor appears to be waning.

* Many companies are making effective efforts to improve productivity.

* Energy use is more efficient than in the past. Oil imports and oil consumption are way down.

This official, who asked not to be named, adds something else, which the White House would be less pleased to hear:

''The benefits of all this cannot be realized, until there is concrete evidence that budget deficits can be brought under control -- or, more fundamentally, that our system of government can work.''

He finds, in going about the country, that ''people are coming to the same conclusion under Reagan that they did under Carter - that no one is in charge of the economy.

''With Carter,'' the official says, ''it was inability to project leadership. Reagan does accomplish that, but cannot seem to translate it into concrete results.''

White House officials, of course, disagree. They claim that the balkiness of Congress stymies progress, which otherwise would be made under the President's economic program.

The victory of ''Latta Two'' -- the Republican-sponsored 1983 budget in the House last week -- is hailed by Treasury Secretary Donald T. Regan as providing ''nearly $300 billion in deficit reductions over the next three years.

''This should encourage the markets, the lenders, that we are capable of government here in Washington,'' Mr. Regan says.

A completed budget process, he says -- based on the Latta Two spending cuts of Latta Two -- ''will bring down interest rates slowly, with the prime rate falling below 14 percent by the end of the year.''

Bankers, apparently, do not agree. Citibank, the nation's second largest, Monday boosted its prime rate back up to 16.5 percent -- several days after Latta Two had passed. That 16.5 prime rate prevails among all major US banks.

Regan's forecast of reduced deficits is based on huge spending cuts in social programs, with which Congress, in the end, may not go along. In other words, uncertainty about the final budget still exists.

''The way interest rates are staying up is an act of levitation, defying logic,'' Regan says. ''No country with an inflation rate below 2 percent has ever before had a real interest rate of 8 to 10 percent.''

The underlying rate of inflation in the United States is thought to be 6 to 7 percent, considerably higher than the 2 percent rise in consumer prices in recent months, to which the Treasury chief referred.

Still, Regan is right. The real rate of interest hangs inexplicably high. One factor is the conviction of lenders and investors that interest rates are bound to stay high, when the government needs to borrow so much capital to pay its debts.

A modest recovery is expected to begin this summer, when a 10 percent tax cut and higher social security benefit payments pour billions of dollars into consumers' hands.

What is questioned is the durability of that recovery. High interest rates, reflecting foreboding about mounting budget deficits, might halt the recovery before it fairly begins.

''It is a shame,'' says the high government official quoted above, ''that the President gives no signal that would indicate his understanding of the financial markets' concern about the huge budget deficits that lie ahead. Those deficits are a terrible drag on the economy -- both in the direct sense of draining billions of dollars from the investment stream and in the sense of fostering uncertainty among investors.''

Ideally, many experts agree, Reagan should be willing to postpone the 10 percent income tax cut due July 1, 1983, thereby promising a big boost in government revenues.

Failing that, he could accept a combination of measures that Latta Two fails to provide - a smaller defense budget (allowing room for more spending to help the poor), higher taxes of some kind, and at least a pledge to trim social security costs down the road.