Even as Congress prepares to vote this week on legislation aimed at balancing the budget by 2002, growing numbers of financial analysts say the nation’s hardy economy will erase federal deficits even sooner.

A minority of these experts, the most optimistic, predict the government will run surpluses by the end of this decade - even without budget-balancing legislation. The last federal surplus was in 1969.

Such projections assume no recession in the next few years, of which nobody can be certain. Even if the predictions come true, all agree that deficits will balloon anew when the huge baby boomers begin retiring in 2008 and drive up Social Security and Medicare costs.

Nonetheless, a surge in federal revenue collections that has confounded the experts has improved the government’s short-term fiscal health dramatically. Riding this tide, this year’s deficit is expected to be $67 billion or less, the fifth consecutive decline since it peaked at $290 billion in 1992.

The government’s two official fiscal analysts - the Congressional Budget Office and the White House Office of Management and Budget - envision budget gaps rising again next year. But in a measure of the widespread belief that inexplicably high revenue collections will continue, those foreseeing an unexpectedly early end to deficits are no longer considered crazy by their colleagues who disagree with them.

“It’s certainly a possibility,” said the more cautious John Youngdahl, an analyst at Goldman, Sachs & Co. “It’s not a wild possibility.”

In an ironic twist of timing, the deficit picture is brightening almost by the month just as lawmakers face a politically painful series of votes on implementing the budget deal between President Clinton and congressional leaders.

Many Democrats oppose slicing projected spending on Medicare and other programs as deeply as the bills propose, while many Republicans are troubled that companion legislation does not cut taxes deeply enough.

Improving budgetary prospects have already made it easier for lawmakers to cram this year’s budget-balancing effort with tax cuts plus spending increases for children’s health and other programs. And although there are no signs that the budget agreement might be collapsing, looming deficits that begin to look smaller can only encourage legislators to demand extra spending and tax reductions.

White House and congressional budget analysts will update their budget forecasts this summer. Neither envisions projecting vanished deficits before 2002.

“I really haven’t heard that, even from optimists,” said Director June O’Neill of the Congressional Budget Office. And Office of Management and Budget spokesman Lawrence Haas said his agency will use “appropriately cautious assumptions” in making its calculations.

The financial world, however, is dotted with advisers who say federal surpluses are coming sooner than expected:

Two weeks ago, the investment bank Lehman Brothers sent clients a newsletter that said: “Even without the recent budget agreement, the U.S. federal government is likely to record budget surpluses by the end of the decade.”

Greg Valliere, managing director of the Charles Schwab Washington Research Group, predicts a surplus in fiscal 1999. Because of the strong economy, “Our analysis is the budget deal is almost like background noise,” he said.

Stanley Collender, who watches the federal budget for Burson-Marsteller, is more conservative but says that with passage of planned budget cuts, “2001 is the latest the budget would be balanced, with a good shot at 2000.”

In addition, Senate Budget Committee Chairman Pete Domenici, R-N.M., said Friday that the surging economy means “we’ll be balanced before 2002 with this agreement.”