In a message characterized as a "heads up alert," intelligence officials warned the State Department, White House, and the intelligence agencies last month that Arab diplomats had suggested that Ambassador Andrew Young meet with a Palestine Liberation Organization official, according to U.S. intelligence sources.

/but -- although such a meeting would have violated U.S. policy -- Carter administration officials did not follow up on the alert by instructing Young not to meet with the PLO officials, nor did they even check to see if the meeting took place, administration officials say.

In fact, Young did carry out the suggestion and -- in a move that eventually cost him his job -- met with the PLO envoy, Zehdi Labib Terzi, on July 26, just hours after the U.N. ambassadors from Kuwait and Syria had first made the suggestion to him.

The "heads up alert" did not reach administration policymakers until July 30 -- four days after the Young-Terzi meeting took place.

It was unclear last night whether the alert ever reached the highest-level officials in the State Department or the White House. State department spokesmen have maintained that the department did not know of the meeting between Young and Terzi until it received a query about the meeting from Newsweek magazine on Aug. 11.

The intelligence alert, dated July 30, referred to suggestions that were made to Young on July 26, at a luncheon meeting at the New York City residence of the ambassador from Kuwait.

In addition to the intelligence alert, there was one other reference in State Department files to what went on in that luncheon meeting, according to a department official. It was a report prepared by Young's own office at the U.S. mission to the United Nations, the source said. However, it could not be learned just how much detail was contained in this report or whether it made any mention of the suggestion that there should be a meeting with the PLO official.

Young maintained this past weekend that the State Department had in its files a detailed, almost verbatim account, dated July 30, of what was said at his meeting with the PLO official on the evening of July 26. Young said he saw the document at the State Department on the day he resigned, Aug. 15. Whether the document he saw was the July 30 intelligence "alert" is unclear, but State Department officials indicate they were one and the same.

State Department officials continued yesterday to deny that the department on July 30 had a detailed account of Young's July 26 meeting with Terzi.

Department spokesman Thomas Reston reiterated his Sunday statement that no account of the meeting was available before Aug. 11 and that on July 30 the department only had information that "a suggestion" had been made about a Young-Terzi meeting, "but not that a meeting had been agreed upon."

A senior department official later amplified Reston's statement by suggesting to reporters that if they checked with Young, the ambassador would not disagree with the statement. However, aides in Young's office in New York would say only that they had "no comment" on what had been said at the State Department.

In private, department officials said the statement had been worked out in consultation with Young on Sunday by Warren M. Christopher, who is acting secretary of state while Cyrus R. Vance is on vacation. These officials argued that Young's refusal to comment was, in effect, a confirmation of their assertion that he would not disagree with the statement.

In addition, Reston also said that the department had checked with the office of the director of central intelligence, which coordinates all U.S. intelligence activities, and had been assured that it does not know of the existence within the U.S. government of an account such as that described by Young.

Elaborating on that point, department sources said Christopher had contacted Frank Carlucci, deputy director of the Central Intelligence Agency, yesterday morning after reading a New York Times report that senior U.S. intelligence officials knew about the substance of Young's meeting with Terzi.

Carlucci, the sources said, reported back that his office had no information to back up such a charge. Other sources within the intelligence community also denied there had been prior knowledge of the meeting; and the Justice Department, which had promised to investigate whether the FBI had been involved, said yesterday that neither the FBI nor any of the other agencies under its control "had any knowledge of the substance, or contents, or even existence" of the meeting.

In short, the thrust of the accounts being offered by State Department and intelligence officials was that on July 30 only one document -- the "heads up alert" -- appeared to exist relating to the Young-Terzi meeting and, according to their descriptions, that document could not be described as a detailed account of an actual meeting between the two.

Instead, the sources said, the document consisted of a four-paragraph intelligence report that on July 26, at a luncheon meeting between Young and two Arab ambassadors at the United Nations, a suggestion was made by the Arab participants that a pretext be found to bring Young and Terzi together.

The sources added that the brief intelligence memo mentioned that Young had expressed concern to his Arab colleagues about an upcoming U.N. Security Council debate on the rights of Palestinians. But, the sources said, there was no detailed elaboration of any positions Young might have outlined to the Arab ambassadors either on behalf of the U.S. government or himself and no indication that he had agreed to the suggestion of a meeting with Terzi.

According to the sources, the intelligence memo was distributed to the White House, the State Department and various intelligence agencies. But they were unable to explain why the account of the July 26 session took four days to reach the State Department or why no one there or at the White House followed up by asking Young whether he had gone ahead and met with Terzi.

Some sources said the four-day lag probably was due to the normal workload process of sifting and distributing large amounts of intelligence information. Other sources suggested that State's failure to check with Young may have been due to an assumption by department officials that the Arabs merely were reiterating their long-standing plea for official U.S. contacts with the PLO and had been given a routine refusal by Young.

Some sources also said that, despite the bureaucracy's apparent failure to find any document other than the intelligence alert, some other piece of paper relating to the Young-Terzi meeting may have existed and come to Young's attention.

Although they stressed that they were speculating, these sources said they could not rule out the possibility that the meeting had been reported to the State Department by someone in Young's U.N. mission or by a foreign intelligence service such as Israel's.

Time magazine, in its current issue, quotes a U.S. government source as claiming that Israeli intelligence agents keep tabs on PLO officials in New York, that as a result of shasowing Terzi they saw Young arrive for the meeting and picked up what was said through clandestine listening devices.

Asked about that assertion yesterday. Reston said: "The U.S. government has no information which would confirm that Israeli intelligence was monitoring the conversation between Ambassador Young and Mr. Terzi."

In addition, several intelligence community sources said it seemed inconceivable to them that, even if the Israelis did obtain information about the meeting, they would pass it along to the State Department or other U.S. officials.

These officials said it would be illogical for the Israelis to take such a step at a time when U.S.-Israeli relations are badly strained over the Palestinian issue and when pressures for disclosure of clandestine surveillance activities within the United States could lead to embarrassing revelations of Israeli activities in this area.