The Carter administration, apparently firm in its resolve that the United States should withdraw from the Summer Olympics in Moscow, will ask the U.S. Olympic Committee (USOC) this weekend to decline its invitation "promptly" so that international support can be rallied for the U.S. position.

The USOC said Thursday that it will comply with the president's requests regarding the Moscow Games, but will make no formal decision on participation until its House of Delegates meets in Colorado Springs April 11-13.

Sources in Washington indicated today that the administration is not willing to wait that long. White House counsel Lloyd Cutler is expected to deliver this message to USOC officials here this weekend.

The deadline for accepting an invitation to Moscow is May 24, but Cutler will ask the USOC to make an irrevocable decision, most likely by the middle of next month, to decline the invitation.

This would require an emergency meeting of the USOC executive board or house of delegates, its final policy making authority. USOC counsel Patrick Sullivan said it would be "very difficult" to convene the house of delegates before April.

The administration thinks a swift and irreversible U.S. decision not to participate in Moscow because of the Soviet invasion of Afghanistan is necessary to muster broad international support for an Olympics boycott.

President Carter reiterated Wednesday that if Soviet troops are not withdrawn by Feb. 20 "neither I nor the American people nor the Congress will support the sending of an Olympics team to Moscow."

An administration aide said today, "Our government's position is 100 percent clear, and there are no loopholes. We think the USOC understands that, or will by the end of the weekend, and will translate it into a prompt decision not to go to Moscow."

Meanwhile, the White House and the State Department are continuing efforts to organize alternate games.

The proposed alternate competitions, probably at multiple sites, are being envisioned for after the Moscow games in an effort to receive sanction for them from the international sports federation affiliated with the International Olympic Committee (IOC). The IOC earlier rejected a proposal to move, cancel or postpone the summer Olympics.

Some IOC members have said that these so-called "Free World Games" would be competitive with the Olympics, and would be denied sanction by the 26 international federations that govern Olympic sports. Athletes competing in any "outlaw" games would be subject to penalties, including suspension.

A State Department official said today, "If we were trying to organize games at the same time as the Olympics, I think the IOC would frown on it and kill it. But we're talking about organizing games after Moscow, and we think it can be done without any penalties imposed on athletes."

The USOC is planning a National Sports Festival this summer for American athletes. USOC President Robert J. Kane opposes alternate international games as disloyal to the IOC.

In other developments, Prime Minister Margaret Thatcher Thursday urged the British Olympic Association not to send athletes to Moscow, and a government spokesman suggested that West Germany will not send a team to Moscow if the United States doesn't.

Prime Minister Malcolm Fraser today told Australian Olympic officials that the United States would not be sending a team to Moscow, and strongly urged them to decide not to participate as well.

"The snowball is gathering momentum slowly, but it definitely is gathering momentum," a State Department official said.

"We were very encouraged by the strong stands" taken by Thatcher and Fraser, the official said, "and we were enormously encouraged by the European Parliament resolution this morning . . . urging each of the nine member nations to advise their national Olympic committees not to go to Moscow. Even though that is not binding, it is a sign that European opinion is swinging toward nonparticipation."