WASHINGTON — Along the hushed, marble corridors of the Federal Reserve Board's graceful old headquarters building here, fears of war and recession seem far away--except inside the second-floor office occupied by Alan Greenspan.

In his private lair, the chairman of the Federal Reserve Board is decidedly on a wartime footing.

With his television set tuned to the Cable News Network, a phone line open to the White House and an aide poised by his elbow to provide the latest economic statistics, Greenspan is playing the role of wartime Washington policy-maker to the hilt.

Indeed, unlike his predecessor, the prickly and standoffish Paul A. Volcker, Greenspan has developed close ties to the White House and has quietly become a key economic adviser to President Bush over the past several months.

Greenspan's influence over White House economic policy became clear during President Bush's State of the Union address Tuesday, when Bush announced that he was tapping Greenspan to lead a new commission to study a controversial proposal to cut the tax rate for capital gains.

The appointment will plunge Greenspan--himself a strong supporter of a cut in capital gains tax rates--directly into the middle of a raging political debate between the President and Congress over tax policy.

By any standard, Fed-watchers say Greenspan is taking on a role that is almost unprecedented in modern times. Most say they cannot recall any time that the Fed chief has been asked to step so directly into the middle of such a political controversy.

"Whenever there are major economic decisions to be made, (Greenspan) is in on them," a delighted Fed official says. "His voice is listened to."

But even before his new capital gains study gets going, it is clear that Greenspan has chosen to side with the Administration in the battle over fiscal policy. Soon after the war began, the Fed chairman signaled he planned to cut interest rates further in order to ease the credit crunch that seems to be prolonging the economic slump.

On Friday, he moved decisively, chopping the Fed's key discount rate to 6% from 6.5%. It was the second time in six weeks that Greenspan had turned to this key anti-recession weapon, the heaviest in the Fed's arsenal.

While such actions may be justified on economic grounds, they also conveniently dovetail with what the Administration wants from the Fed. Treasury Secretary Nicholas F. Brady, who frequently criticized Greenspan last year for not moving quickly enough, has been noticeably silent on Fed policy.