President Reagan, nearing a decision on whether to reappoint Paul A. Volcker chairman of the Federal Reserve Board, met privately in the residential quarters of the White House with Volcker this week, according to administration officials. They said the only candidates being considered to head the nation's central bank are Volcker and economist Alan Greenspan.

Volcker requested the meeting with Reagan, which was held late Monday afternoon before Volcker attended a Public Broadcasting Service television taping on the White House South Lawn, officials reported.

The officials said that the president and the Federal Reserve chief met alone and discussed the pending decision on Volcker's term, as well as economic subjects. They would not comment further yesterday, except to say that Reagan has not yet made a decision.

But that decision is expected shortly, perhaps within the next few days. Volcker's term expires Aug. 5.

The decision on whether to reappoint Volcker may be the most important economic choice Reagan makes this year. The deliberations have been conducted at the highest levels of the White House and under extreme secrecy.

"As you can imagine, this is very delicate," one official said yesterday.

Although administration officials originally suggested that a half-dozen possible replacements for Volcker were under consideration, they said yesterday that the only likely choices are Volcker and Greenspan. That apparently excludes Preston Martin, a California Republican whom Reagan appointed vice-chairman of the central bank, from consideration for the top position. "It's a 50-50 proposition," one presidential adviser said of the choice Reagan now faces between Greenspan and Volcker. That official said it is "a very close call."

"It's unpredictable right now," added another official.

Several officials said that the choice between Volcker and Greenspan is essentially not one of policy, since both could be expected to follow generally the same path. Rather, the decision is being discussed at the staff level in political as much as economic terms.

Some officials have argued that Reagan should appoint his own man to head the institution that controls the nation's money supply and influences interest rates and the overall level of economic activity. These officials are pushing for Greenspan, who earned high marks in the White House for his work as the Reagan-appointed chairman of the recent Social Security advisory commission.

"The Reaganauts are lining up behind Greenspan," said one official. This pressure is building despite the fact that Greenspan was chairman of the Council of Economic Advisers in the Ford White House, at a time when Reagan was running against Ford, the official said.

But there has also been pressure building for Volcker. Much of it has come from the business and financial community, where Volcker is highly regarded for his efforts to control inflation.

The Federal Reserve chairman also is being backed by administration officials who think his reappointment would be reassuring to the financial markets.

There appears to be a split of opinion among Reagan's top economic advisers. Treasury Secretary Donald T. Regan is known to think that the president should replace Volcker, if a suitable replacement can be found.

Office of Management and Budget director David A. Stockman is known to think highly of Greenspan, but his second choice would be Volcker. Martin Feldstein, chairman of the Council of Economic Advisers, is believed to support Volcker.

The tall, cigar-smoking Volcker has has become a symbol of both the high interest rates that helped throw the economy into the worst recession since World War II and the largely successful battle against inflation.

Although the decision on his reappointment is largely focused on the future course of the economy and not the past, some officials think that by dumping Volcker the president could also unload responsibility for the hard economic times that have become a political liability for him and still take credit for the progress against inflation.

But more important to the White House now is what course the next Fed chairman will take in 1984 if Reagan runs for reelection. Some officials are uncertain to what degree Greenspan would attempt to be independent from the president if difficult choices had to be made on the money supply, interest rates and inflation in the thick of the presidential campaign.

A source close to Volcker said that the Fed chief feels he still has some "unfinished business" in the troubled international debt situation and would like more time, perhaps a year and a half, to deal with it.

But it could not be learned whether he has made this argument to the president. Volcker could not be reached for comment yesterday and traditionally does not comment on his private meetings with the president.