President Carter is willing to convene a meeting of America's major allies to discuss ways of keeping oil moving through the Persian Gulf if ship traffic is threatened by the way between Iraq and Iran, the White House announced yesterday.

But administration officials sought to play down the significance of Carter's office and denied that a joint military move to ensure free passage in the gulf is imminent or likely.

At the same time, in a meeting yesterday with Milwaukee television reporters, Carter said that "whatever is required" to keep the Strait of Hormuz open "will be done." However, he refused to discuss specifies of what that might involve.

The developments came amide multiplying rumors that the United States is trying to promote creation of an international naval task force to prevent possible closure of the strait, the waterway commanding the entrance to the gulf.

These rumors were brought to a head by reporters from Japan yesterday that Carter had sent letters to West Germany, France, Britain, Italy and Japan proposing a meeting on how to deal with the situation.

In response the White House issued a statement saying the president has "exchanged views with key friends and allies on a wide range of issues related to the conflict." It added:

"The United States has indicated that it would be willing to host a meeting to review these issues if that should seem desirable. If it is determined that a meeting of experts is required, we will work out timing and location. No such meeting has been set. In the meantime, our consultants are continuing."

Administration officials refused to discuss details of these talks. However, the White House press secretary Jody Powell went out of his way to stress that since the talks began, the movement of tankers in and out of the gulf has remained "virtually normal."

Although, Iraqi and Iranian ports are closed, shipments continue from the other oil-exporting countries in the gulf, Powell said. He added that there was no justification at this time for "scare stories" about severe oil shortages being triggered by the conflict.

Other administration sources, who asked not to be identified, said that earlier in the week, there had been much greater concern about possible trouble at Hormuz. At that time, the sources continued the administration initiated intensive discussions with the five countries named in the reports from Japan about possible contingency planning if the strait should be closed. f

According to the sources, these discussions were conducted primarily by Secretary of State Edmund S. Muskie during his meetings with the allied foreign ministers at the United Nations General Assembly session in New York.

The U.S. aim, the sources said, was not to propose a specific course of action like formation of a joint naval task force but to sound out the allies on their ideas.

As the fighting has progressed, though, the U.S. analysis of the situation has swung toward the view that it might be possible to halt the conflict within a short time. In that case, the need to safeguard shipping in the gulf would become moot.

However, the sources continued, while the administration does not put as high a priority on contingency planning as it did earlier in the week, U.S. policy makers still think it would be prudent to continue discussions with the allies. It was that thinking, they said, that prompted the White House offer to host a meeting if the other countries are agreeable.

But, although the other countries get the bulk of their oil from the Persian Gulf, their initial reactions to the U.S. suggestion were extremely guarded and mixed.

In Bonn, West German Chancellor Helmet Schmidt admitted at a news conference that he he had been contacted about a Washington meeting but said his country's constitution forbids any form of German military presence outside the defense zone of the North Atlantic Treaty Organization.

In Britain, a spokesman for Prime Minister Margaret Thatcher confirmed she had received a message from Carter but refused to reveal the contents. Government sources in Japan, which gets more than 70 percent of its oil from the gulf region, said they had agreed in principle to attend a Washington meeting.

Sources in France said there was an exchange of messages between Carter and French President Valery Giscard d'Estaing on the necessity of preserving free navigation in the gulf. But, the sources aded, there was never an American proposal for a six-nation conference or gulf task force.

Australian Prime Minister Malcolm Fraser said the United States had asked his nation about possible participation in a joint peace-keeping operation, but that he did not regard it as a formal request.

Officials in all these countries echoed their U.S. counterparts in expressing encouragement that shipping so far has not been disrupted and optimism that the fighting might soon be halted. Like the United States, they have been working at the United Nations and elsewhere to encourage an initiative by the Islamic bloc of nations to promote a cease-fire between Iraq and Iran.

Carter's Republican challenger for the presidency, Ronald Reagan, yesterday reversed a longstanding policy and accepted a White House offer for an intelligence briefing on the Iran-Iraq conflict.

On his campaign plane en route from Portland to Los Angeles, Reagan issued a statement, which said: "Ambassador [George] Bush and I are accepting this offer because of the delicate world situation and the threat to world peace and stability the conflict poses. I am determined to do and say nothing to exacerbate the situation or hurt in any way our efforts to bring about a satisfactory ending to the fighting."

Until yesterday, Reagan had refused offers for White House briefings on the grounds they might co-opt his campaign positions. But his spokesman, Lyn Nofziger, said he was changing his stance because of the danger of the current crisis.