The Reagan administration refused yesterday to confirm officially that a U.S. Navy fighter fired missiles at a suspected Iranian warplane last weekend, saying that to discuss publicly what had happened could encourage violent retaliation by Iran.

White House spokesman Marlin Fitzwater, following what he said was the lead of Defense Secretary Caspar W. Weinberger, declined to confirm that the incident had occurred. But moments later, he told reporters that President Reagan was informed "soon after the incident happened" Saturday. Asked plan.

what incident he was talking about, Fitzwater said with a wink, "The incident I'm not confirming."

Weinberger, in a breakfast meeting with reporters yesterday, also refused confirmation, but said he would be willing to provide additional information about U.S. operations in the Persian Gulf once it was possible to do so without risking "injury to the safety of the people doing the job."

Officials cited various motives for what one of them called the "word games we're playing." These included Pentagon sensitivity to the failure of the U.S. fighter to hit its target, White House political worries about congressional attempts to get Reagan to invoke the War Powers Resolution, and a widely shared administration concern that the news media are providing too many operational details about actions in the Persian Gulf, where U.S. warships are providing escort for Kuwaiti supertankers flying the American flag.

"In addition there is a remote possibility that the aircraft wasn't Iranian or even that it wasn't an aircraft and we haven't heard anything from Iran so we don't want to escalate this further," an administration official said.

Some of the Defense Department's top military leaders reportedly urged that the incident not be disclosed because of "potential embarrassment," according to several administration sources. These sources said Weinberger was persuaded by some members of the Joint Chiefs of Staff to quash information on the incident shortly after it occurred on Saturday.

The Navy was embarrassed July 24, when the supertanker Bridgeton hit a mine on the first U.S. convoy of Kuwaiti tankers in the Persian Gulf.

Weinberger yesterday refused to elaborate on the missile-firing episode, saying "No. I could, however, point out that a very recent story attributed to anonymous sources turned out to be very wrong and I would make the same point I always do, that anonymous sources aren't very good sources."

Weinberger was referring to reports by The Washington Post and other news organizations late last week quoting unnamed sources who said the escort operation had been postponed for up to a week. But the next convoy began Saturday morning, a day after those reports.

"I do think the heavy reliance on these people who decline to be named and feed out alleged information is not a very healthy way to deal with a situation in which there is a very considerable amount of potential for risk with our personnel," Weinberger said. Fitzwater made a similar point at a briefing Monday, saying that reporters used anonymous sources "at their own risk."

While Weinberger has ordered his staff not to discuss operational details in advance of the missions, several administration officials privately criticized the decision to withhold details of the missile firings. The administration a week ago attempted to cover up another incident in which U.S. military officials believed they had detected unusual signs of activity at a previously unknown Silkworm missile launching site along the Strait of Hormuz. It turned out to be a "false alarm," sources said.

Pentagon uncertainty about the facts of the latest incident, and embarrassment that the missiles had missed their target, were magnified at the White House by political considerations.

The primary White House concern was that an American hostile act would make a case for the congressional position that Reagan should invoke the War Powers Resolution to cover U.S. naval deployments in the gulf. White House chief of staff Howard H. Baker Jr. initially supported reliance on the War Powers legislation, but Reagan accepted the Pentagon view that this was unnecessary.

"Every time there's an incident of this kind, it becomes more difficult to argue that U.S. forces are not being placed in a hostile situation," a White House official acknowledged.

The War Powers Resolution is intended to make deployment of American forces in hostile situations subject to congressional approval. Once the president notifies Congress that U.S. forces are being introduced "into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances," Congress has to agree to any deployment of forces beyond 60 days.

Underlying the administration's policy of secrecy is a conviction, which an official said is shared "by the Navy and the president," that too much information about the operations is appearing in the media. "We've shut the door on the leaks, and we're going to try to keep it shut," an official said yesterday.

The issue of timely disclosure of military operations has been a sore point between the Reagan administration and the media ever since the 1983 U.S. invasion of Grenada. As reports of the unannounced invasion were being broadcast by Caribbean radio, some White House officials called reports of the impending invasion "preposterous."

After Grenada, the Pentagon and media representatives worked out guidelines for future operations, which provided for the kind of press pool that accompanied the U.S. Navy on its first gulf convoy last month.