The United States is experiencing "a significant economic slowdown" this quarter that is likely to continue into the first three months of 1991 and perhaps beyond, Treasury Secretary Nicholas T. Brady said yesterday, but he refused to characterize the slump as a recession.

"What's the point of getting ahead of the game?" he said. "Let's watch and see. Maybe it will be. I don't think it's the end of the world even if we have a recession -- we'll pull back out of it. No big deal."

Until now, top administration officials have acknowledged only that the economy is declining this quarter.

The Treasury secretary, interviewed on the NBC television program "Meet the Press," predicted that during 1991 the economy will "turn around and we'll be back on the growth path."

To encourage that turnaround, Brady said the Federal Reserve should cut interest rates.

"There's ample room for further reduction in interest rates," he said.

Meanwhile, Council of Economic Advisers Chairman Michael Boskin, who appeared on ABC-TV's "This Week with David Brinkley," agreed that "the best guess is the economy will be reviving sometime next year."

"Whether we'll have a recession that lasts several quarters -- it should be mild and brief," he said. "If we do {have a recession}, or we narrowly skirt it, remains to be seen."

Boskin said the Federal Reserve should "be looking forward to see what the economy is likely to do. And if it looks like the economy is going to be in a sluggish state for some time, they ought to be continuing the kinds of steps they've taken," which have included cuts in short-term interest rates and a reduction in the amount of money banks have to keep in non-interest bearing deposits at the Fed. The latter move should directly boost bank profits next year.

Brady said President Bush's fiscal 1992 budget, which will be sent to Congress in early February, will propose additional measures to help get the economy out of its slump. He declined to give any details.

The Treasury secretary hinted that one of Bush's favorite ideas, a cut in capital gains taxes, might be foreclosed by the budget law passed last month. In that law, any revenue lost because of a tax cut has to be offset with higher taxes elsewhere or a cut in spending on entitlement programs, such as Social Security.

Brady indicated that since Congress's Joint Committee on Taxation, which he described as "controlled by the Democrats," believes a cut in the capital gains tax rate would lose revenue, there is "an automatic formula which makes you produce taxes elsewhere."

"And the president is not going to raise taxes in 1991 {or} fiscal 1992," Brady said.

Several economists who also were interviewed by ABC said the economy is clearly in a recession and questioned whether it will be quite as mild and shallow as Boskin suggested.

One of them, Henry Kaufman, formerly a managing director of Salomon Brothers Inc. and now a consultant, predicted the economy would decline 2 percent before the recession ends sometime next year. Furthermore, Kaufman said, once the recession is over the recovery will be weak.

"The capacity to recover in this economic setback to the type of recovery we've had in the past is very poor because we have extraordinary financial impediments here, unlike any other previous cyclical situation in the post-World War II period," Kaufman said.

Among those impediments, he said, are "a massive debt overload among borrowers" and a "whole range of financial institutions" that have lost so much money that they are not in a position to step up their lending activity when a recovery begins.