If Reagan won't chop the deficit, will anyone?

Time is getting short and there may be a budget debacle.

That's the warning some Democratic and Republican leaders of Congress are sending the White House. The United States hasn't had a balanced budget since 1969; some estimate the deficit next year as high as $150 billion.

The US is the only democracy that separates executive and legislative budget functions and it is Congress, not the president, that appropriates funds and determines how much is spent and where. The president sends original budget proposals to Congress, the size of a telephone book. If Congress and the president can't agree, a deadlock develops, as now.

In 1974, Congress passed a reform act to coordinate the budget process, but this procedure itself, like a creaky bridge, may collapse.

''Only quick solution of the current Congress-White House deadlock can save it; there are too many economic Falkland Islands ahead,'' said Congressional Joint Economic Committee chairman Henry S. Reuss (D) of Wisconsin to a group of reporters Monday.

The same warning comes from Senate Finance Committee chairman Robert Dole (R) of Kansas, an influential figure on the Republican side. He urges a broad, quick compromise between President Reagan and House Speaker Thomas P. (Tip) O'Neill Jr. He told NBC's ''Today'' show that he thinks chances are only 50-50 of agreement.

President Reagan's personality, prestige, and power figure in the current debate. He has made reduced income taxes and higher defense spending key features of his policy. Inflation has dropped dramatically as the quasi-independent Federal Reserve Board slams on the brakes of high interest rates. But these, in turn, cause anguish to industry, builders and agriculture.

Soon comes the crunch. ''The public isn't mad at the President, but think his economic program is a dud,'' said Representative Reuss.

Without criticizing President Reagan, Senator Dole said the administration program needs ''billions and billions of new taxes.'' To resolve the deadlock, he said ''it's going to take the President and Speaker sitting down together and saying, 'OK, we've got a problem. We've got to get interest rates down, deficits down, how do we do it?' '' Failure to reach agreement, Dole warned both sides, could bring national anger.

Cries of warning grow louder in Washington. Herbert Stein, a conservative economist writes, ''If now the most classical, hard-line conservative president in 50 years accepts indefinite deferral of a balanced budget . . . who will any longer be inhibited by fear of deficits?'' Two Republican spokesmen who will shortly retire from Congress, Rep. John Rhodes of Arizona, formerly Republican leader in the House, and Rep. Lincoln Marks of Pennsylvania, both criticize current policies. Mr. Rhodes's differences are over big defense items, Mr. Marks's are across the board.

Congress ponders a budget-balancing amendment to the Constitution. The Senate Judiciary Committee approved it 11 to 5 and Mr. Reagan expressed sympathy. But to become law, it must have two-thirds majority in Senate and House, and approval by three-fourths of the states, which is unlikely.

To many, Reagan's willingness for immediate budget compromise has become a touchstone of his administration. The White House stresses that inflation is sinking. It charges that the press overemphasizes cuts in Federal aid to the poor.