ALAN GREENSPAN, chairman of the Federal Reserve Board, bluntly told the Reagan administration this week to stop leaning on him to lower interest rates. A reporter then asked President Reagan at his press conference whether he still had confidence in Mr. Greenspan. The president emphatically replied that he does -- "and I'm going to have to find out what this is all about that you're talking about because nothing of that kind has been directed to me."

Nothing? Some of it appears over Mr. Reagan's signature in his annual Economic Message to Congress, delivered last Friday. There he, or someone using his name, observed that the prospects for growth in the immediate future have been diminished not only by the stock market crash but also by "the increase in interest rates and tightening of monetary policy during 1987." The president has never pretended to pay much attention to the economic statements that, like this one, the White House is required to produce periodically. But when people talk about the current campaign of needling the Federal Reserve, this is the sort of thing they have in mind. There's more of it, carefully qualified but unambiguous, in the accompanying report by the president's Council of Economic Advisers. The council's chairman, Beryl W. Sprinkel, has earned a reputation as a zealous advocate of monetarist theory and an inveterate critic of the Federal Reserve.

There was also the letter that an assistant secretary of the Treasury, Michael R. Darby, sent last month to most of the Federal Reserve Board and its Open Market Committee, suggesting that too-tight monetary policy was pushing the country into a slowdown and perhaps a recession. If Mr. Sprinkel and his allies continue this campaign, Mr. Greenspan observed, the result may well be a policy tighter than otherwise necessary. The Federal Reserve would be compelled to lean over backward to demonstrate to the financial markets that it is not being manipulated by the administration and its desire for election-year prosperity.

The Council of Economic Advisers does not at present have any visible impact on actual policy. But even the hint of a dispute between the White House and the Federal Reserve rattles markets where borrowers, lenders and traders have a great deal of money at stake. Economic theories are hardly the issue. It is never helpful to the economy to leave investors and businessmen in doubt as to who -- if anyone -- is making the administration's decisions.