The intelligence community's warning of an impending attack on West Berlin nightclubs frequented by American GIs was not given top priority because of an apparent communications foul-up, U.S. officials said yesterday on the basis of recent briefings by the Central Intelligence Agency.

Officials who heard the briefings said the warning went through the military command at lower levels rather than to top commanders, as is the case with a "critic" message considered extremely important and demanding attention.

A bomb went off in the La Belle nightclub in West Berlin on April 5, killing a U.S. Army sergeant and a Turkish woman and injuring 204 persons. Officials who have been briefed said the warning was specific enough and sent out in time to enable the military to vacate the La Belle and other nightclubs before the bomb went off.

The Pentagon disputes this, declaring that the warnings were not specific but saying it had taken action that almost averted the tragedy.

The prospect of explaining a breakdown in communications between the intelligence community and military commands comes as the Reagan administration is seeking to persuade its allies that Libya was behind the Berlin terrorist bombing and to accept a retaliatory strike against Libya, if the administration decides to launch one.

In an effort to deal with growing concern among U.S. allies, the administration secretly dispatched U.N. Ambassador Vernon Walters as a special emissary to Western European nations.

The State Department announced that Walters met in London yesterday with British Prime Minister Margaret Thatcher and will visit "several other allied countries" in the days ahead.

Officials confirmed that Walters will be in Rome Monday to see Italian Prime Minister Bettino Craxi but released no other details of Walters' itinerary.

Walters, a former deputy director of the CIA, has often been used for confidential discussions with heads of state, especially when highly classified intelligence was involved.

At the Pentagon yesterday, planners continued to refine bombing plans, in the event that President Reagan should decide to order military retaliation. Sources said there is general agreement in the White House that the military route should be pursued against the Libyans, but there has been no decision to launch a strike.

The aircraft carriers USS America and USS Coral Sea were circling in the central Mediterranean yesterday, with some bombers loaded with munitions, sources said. The ships have about 270 aircraft on board, which are in easy striking distance of Libya. But military plans have been put on hold, apparently pending U.S. consultation with allied countries.

One Pentagon analysis indicates that hundreds of Libyans could be killed under some military options being considered, sources said.

Reagan said at his news conference last week that he is prepared to retaliate against Libya if there is proof that the Libyans were behind the Berlin bombing.

NATO commander Gen. Bernard W. Rogers said there is "indisputable evidence" linking Libya to the attack. And on Friday, White House chief of staff Donald T. Regan said the administration was "coming close" to concluding that Libya is to blame.

The new issue about whether the warning of attacks on the West Berlin entertainment district centers on how it was classified, when it was sent and what actions were taken by military commanders when they received it.

Pentagon spokesman Fred S. Hoffman said yesterday that he had "no knowledge" about what priority the warning message was given and thus would not comment beyond what the Pentagon has already said.

On Friday the Pentagon said, "There was no advance warning of attack against La Belle or any other specific site. We understand there were advance reports of possible attack against unspecified locations in West Berlin where American servicemen gather. Security officers had begun to take precautions and warned U.S. personnel about possible danger, including at various nightspots."

Military officials complain they are flooded with warnings of terrorist attacks and cannont repond to all of them and complete their missions.

If there was a communication breakdown, as several officials claim on the basis of CIA briefings, it could have occurred anywhere from the transmission center at the Pentagon to the theater command centers scattered all over Europe.

The standard route for such a message would be from the Joint Chiefs of Staff at the Pentagon to NATO commander Rogers in Mons, Belgium; to his deputy in Stuttgart, West Germany; to the commander of Navy forces in Europe in London; to the commander of the 6th Fleet in Gaeta, Italy, and then to the ships in the Mediterranean.

Twice before in the last two decades there have been monumental breakdowns in sending out warning messages. In 1967 the Joint Chiefs of Staff drafted a message ordering the spy ship USS Liberty to move farther away from the Egyptian coast where it was eavesdropping on the Arab-Israeli war. The message was downgraded before it was sent through the chain and did not reach the Liberty in time. Israel attacked and almost sank the ship. Thirty-four Americans were killed.

In 1967 a warning destined for the spy ship USS Pueblo also went astray in the Pentagon and was not acted on in time to avoid the ship's capture by North Korea in 1968.

The Walters mission to Europe was described by administration spokesmen as a trip to discuss "the threat of terrorism" is a follow-up to a tour of allied capitals by Deputy Secretary of State John C. Whitehead in January.

"We are particularly concerned that American tourists, diplomats and servicemen are being targeted and brutally murdered in Europe," White House spokesman Peter Roussel said. "We want to work with European law enforcement and security authorities to reduce the risk."

The administration said Attorney General Edwin Meese III is scheduled to go to Europe at the end of April for another round of meetings on terrorism. Roussel said that before Meese's trip, the administration was sending counterterrorist experts from the State and Justice departments and other agencies to confer with their European counterparts. Those meetings, he said, are to be held Monday and Tuesday.