ON THE SUBJECT of the Federal Reserve Board and interest rates, President Reagan is a study in ambivalence. He doesn't care to oppose the board's present policy explicitly, since it's by far the country's most effective restraint on inflation. But, as at this week's press conference, he takes every opportunity to let everybody know that he isn't responsible for the Federal Reserve's conduct.

The Federal Reserve is emerging as the focus of the administration's well-founded anxieties that when the recession ends, presumably some time this spring, the recovery will quickly be strangled by very high interest rates. That would leave unemployment stuck at a spectacular level, with an election coming. The conventional remedy is to lean on the Federal Reserve to provide more reserves to the commercial banks, inducing them to lend more and, in the process, reducing interest. But that won't work this winter, just as it hasn't worked for the past two winters.

The financial markets are now dominated by institutions that have lost very large amounts of money, over the past decade, by repeatedly underestimating the heights to which inflation would go. If the lenders were to sense that the Federal Reserve was collaborating in another big election-year boom with the usual inflationary hangover, something like panic would grip the financial world--and interest would rise, not fall. That's what happened in early 1980, throwing the economy into a short, painful recession. With minor variations, the same thing has happened twice since then--in December 1980 and again last spring. This record strongly suggests that the Federal Reserve has very little control over interest. It can do nothing to lower rates, but any significant departure from its present posture will raise them. The rates are currently being set primarily by the lenders' fears of inflation. There is no other explanation for their behavior in recent weeks, when they have been rising while the country fell sharply into recession.

This dilemma of the rates probably is insoluble, as long as the White House promises nothing but large and continuing deficits that aggravate fears of high and continuing inflation. Sensible budget strategy at the White House can take some of the pressure off monetary policy and interest. Until it does, the present pattern of repeated slumps and rising unemployment is likely to persist. That's another reason for the extraordinary importance of the budget plans, for next year and the years beyond, that Mr. Reagan will publish early next month.