When the International Olympic Committee announced its intention Tuesday to go ahead as scheduled with this summer's Olympic Games in Moscow despite the Soviet invasion of Afghanistan, an Italian journalist here remarked wryly: "The children have said they will play. Now we will see what the adults say."

The "adults" of course, are the governments of the United States, its allies, and Third World nations. These governments, regardless of the IOC's rules and protestations to the contrary, will have a profound influence on the decisions made by their respective national Olympic committees about participating in the Moscow Games.

Within an hour of the IOC's decision, White House press secretary Jody Powell issued this statement: "We regret the decision of the international Olympic Committee to conduct the 1980 Summer Olympic Games in Moscow, and rejecting the proposal of the United States Olympic Committee to transfer, postpone or cancel the Games.

"Under these circumstances, neither the president, the Congress, nor the American people can support the sending of the United States team to Moscow this summer. The president urges the United States Olympic Committee to reach a prompt decision against sending its team to the Games.

"The United States is working with a number of other like-minded governments to take similar action, and to consider the practicability of conducting other international games for teams which do not go to Moscow."

The British Foreign Office today issued a tough statement supporting President Carter's position, and said it would convey its objections to British participation in Moscow to the British Olympic Association before it meets to consider the matter on March 4.

The British government "will continue to consult with the growing number of countries that share this view and will consider with them what options are open to us following this decision," the statement said.

Other Western governments are expected to make similar declarations in the near future, and to put pressure on their national Olympic committees not to send teams to Moscow.

At his Washington news conference tonight, Carter reaffirmed that if Soviet troops are not withdrawn from Afghanistan by Feb. 20, he will call on American athletes to boycott Moscow. He said he saw no possibility he would change his mind if the Soviets carry out a withdrawal between that deadline and May 24.

A Soviet pullout from Afghanistan by Feb. 20 now appears to be a physical as well as political impossibility.

The U.S. Olympic Committee, which argued that Moscow was an unsuitable host for Games dedicated to peace and goodwill "under present circumstances," urged the IOC to put off a decision for a month or two, in the hope that those circumstances would change. But the IOC president, Lord Killanin, said that "any form of delay would have been possibly a sign of weakness, or of indecision."

Instead, the IOC proclaimed that "the Games will be held in Moscow and attended by all those who accept invitations." Killanin said the IOC had no rules or provisions for calling off the Games because of sparse participation, though he did leave open the possibility of reconsidering postponement or cancellation if a substantial number of national Olympic committees conveyed their intention to reject invitations.

A State Department official said today that "about 50 governments," of the 140 to which Carter sent messages concerning the Olympics, have indicated, publicly or privately, that they favor declining invitations to the Moscow Games.

The deadline for accepting invitations to Moscow is May 24, eight weeks before the scheduled July 19 opening of the Games, at which time national Olympic Committees must inform the Moscow Olympic Organizing Committee of the sports and events in which they plan to enter teams.

The Olympic committees in most countries that are being pressured by their governments to withdraw, including the USOC, would like to wait as long as possible -- "hoping against hope," as USOC President Robert J. Kane put it, that the Soviet government makes enough peaceful gestures that going to Moscow for the Games can again be "consistent with the national interest."

The Carter administration, despite recent indications by White House counsel Lloyd Cutler to the contrary, now seems in a mood to request the USOC "to reach a prompt decision against sending its team to the Games."

The attitude in Washington is that a firm and irrevocable commitment by the United States not to participate in Moscow would help immensely in lining up international support, and might yet force the IOC to strip Moscow of the Games, least they become merely a Soviet bloc party.

There is also widespread conviction in Washington, contrary to the opinion of experienced sports organizers, that alternative "Free World Games" could be organized this summer if the task is undertaken immediately.

The USOC is preparing contingency plans for a National Sports Festival for U.S. Olympians if they do not go to Moscow, but will not invite international participation. Any athlete who competes in international games not sanctioned by the international sports federations affiliated with the IOC is subject to severe sanctions, including suspension.

If the USOC is asked for a decision before its House of Delegates meets on April 12-13, as now seems inevitable, it can be expected to announce that it will decline its invitation to Moscow if Soviet troops remain in Afghanistan on May 24, and to put the invitation in its breast pocket until that date.

If the Soviet Union has made peaceful overtures by then, and American public opinion has swung to favor U.S. participation in the Olympics, the Carter administration might change its "adamant" position. After all, this is an election year, and elections are the games "adults" play.