Washington — Treasury Secretary Donald T. Regan has stretched out a tightrope along which, in the administration's view, the Federal Reserve Board should walk in coming months - no matter who the next Fed chairman may be.
The No. 1 objective of the central bank, Mr. Regan told reporters at breakfast Thursday, must be to continue to fight inflation.
At the same time, Regan said, the Federal Reserve should supply ''enough money to sustain the economic recovery, a sensible supply of money, given the Fed's anti-inflationary stance.''
That fine line the Treasury chief leaves to the chairman of the Fed and his fellow governors to define - a tricky job, since too much money will breed inflation, too little may throttle the recovery.
Meanwhile, the economy is generating so much steam, Regan said, that on July 15 it is ''entirely probable'' that the White House will boost its forecast of how much it will grow this year.
Originally the administration called for a 3.1 percent growth rate from the fourth quarter of 1982 to the fourth quarter of 1983. That was revised to 4.7 percent, which now appears to be too low, said Regan.
Should the Fed begin now to tighten the monetary reins, given the torrid growth of the nation's basic money supply in recent months?
''No,'' the Treasury chief said - not until all the June figures are in on the growth of M-1, to determine whether or not the high April and May growth of that measurement of the money supply was an aberration.
M-1 measures the total of cash in circulation throughout the United States, plus checking accounts of all kinds, including interest-bearing NOW accounts.
Concern over growth of the money supply, coupled with huge budget deficits in the years ahead, is already prompting investors to push interest rates up.
''The Treasury,'' said Regan, ''now is paying a little over 8.5 percent to borrow short-term money. Over the last eight months the rate has varied between 8 and 8.75 percent.''
He said the anticipated inflation rate, as measured by the gross national product deflator - a broader measurement than the consumer price index - is 4 to 5 percent. ''So,'' he concludes, ''the spread is not large.''
Lenders, in other words, are satisfied with a 3 to 4 percent real interest rate on short-term loans. The ''real'' rate of return on a lender's money is the nominal interest rate, in this case about 8.5 percent, minus the anticipated inflation rate over the life of the loan.
''But,'' he said, ''on longer-term issues the Treasury is paying 10.5 percent'' to borrow. He agreed that this reflects uneasiness on Wall Street over the implications of a swelling money supply and soaring deficits. ''In the short term,'' he said, ''we can get along with high deficits without inflation. In the long run, we cannot.''
So much slack now exists within the economy, he said - raw materials in plentiful supply, factories operating far below capacity, unemployment high - that lendable capital is ample, despite record borrowing demands by the Treasury.
When private borrowing increases, however, as the recovery heats up, competition for capital among government, business, and individuals will put a squeeze on the supply of money, driving up interest rates.
Two or three years down the road, Regan said, ''we will get overcrowding,'' unless the deficits shrink.
Analysts in and out of government support this diagnosis. Where many experts part company with the administration is over what to do about the deficits. ''We need a tax increase now,'' says Herbert Stein, chief economic adviser to former President Nixon, ''for the long-term purpose of reducing deficits and increasing the capital stock. There should be a $50 billion-a-year (tax) increase.''
''The overwhelming message,'' says economist Rudolph G. Penner, also an adviser to Republican presidents, ''is that we need tax increases. We can't wait until 1986 - we should start in 1984.''
President Reagan, by contrast, opposes tax increases until fiscal 1986 and then only if certain conditions are met, including passage by Congress of all domestic spending cuts requested by the White House.
Regan refused to talk about whom President Reagan will appoint as Fed chief when chairman Paul A. Volcker's term ends Aug. 5.
Why does the financial community support the reappointment of Mr. Volcker? ''By and large,'' Regan said, ''Wall Street supports anyone in authority who is stable, cautious, and anti-inflationary in policy.''