U.N. Ambassador Andrew Young has promised to stay away from substantive contacts with the Palestine Liberation Organization while presiding over the U.N. Security Council debate on Palestine starting next week, the State Department said yesterday.

Spokesman Thomas Reston said Young had authorized and agrees with a statement drafted late Thursday referring to the restrictions on Young's role as Security Council president in an awkward and delicate situation.

Reston confirmed that Young will retain his post as U.S. ambassador to the United Nations at least for the rest of this month, because his successor will not have been nominated and confirmed by the Senate before then.

The State Department made it clear that Young will be expected to cast a U.S veto of any Palestinian rights resolution unacceptable to the Carter administration, whether or not the resigned ambassador personally agrees with it.

With the PLO and Arab states insisting on a strong U.N. statement backing an independent Palestinian state, the chances for a veto appear strong.

Under his U.S. hat, Young also will be expected to lobby for an American resolution that is being tried out on Israel and Egypt by special Mideast negotiator Robert S. Strauss on his current trip to the area.

Young's international hat results from a series of strange coincidences. As the luck of rotation would have it, the U.S. ambassador this month is serving as president of the U.N. Security Council.

And as the result of the postponement of a scheduled debate, the delay that Young was seeking in his July 26 meeting with the representative of the PLO, the Palestinian issue is due to come before the Security Council, with Young presiding, beginning next Friday.

In his role as Security Council president, Young is expected to call upon the PLO observer, Zahdi Labib Terzi, when the Palestinian asks to speak. But the State Department said "other dealings" with the PLO are not anticipated.

Terzi, whose meeting with Young began the controversy leading to Young's resignation, told reporters in New York that he expects Young to be available to him "if there is something to warrant it," despite any Washington declaration to the contrary.

Terzi said he did not propose to make an issue of the matter, but "in principle, we will insist that he be available" as an officer of the international body.

Before the State Department restrictions were issued late Thursday, following consultations with Young. Young said that if Terzi asked him for an appointment in his capacity as Security Council president "it would be unconscionable to turn him down."

Diplomatic consultations about the forthcoming Palestinian debate are expected to begin early next week, with Young taking a major role. A U.N. official said there is no indication at the moment that the debate will be postponed again.

In an interview published in The Atlanta Constitution this week, Young expressed disagreement with a wide range of administration policies, from normalization of relations with Vietnam to military budget increases and the MX missile. The interview was conducted by reporter Andy Alexander Tuesday morning, shortly before a State Department briefing disclosing that Young had reversed his story that his July 26 meeting with Terzi had been accidental and nonsubstantive.

Saying that he would continue to campaign on weekends for President Carter's reelection, Young indicated that, at that point, he still expected to continue in his job.

Young told his interviewer that he had become "too controversial" to be considered for secretary of state, but not too controversial to be tapped as a vice presidential candidate. Except for his commitment to campaign for Carter in 1980, Young said he might be tempted to run next year for mayor of Atlanta or for the Senate seat now held by Herman E. Talmadge (D-Ga.).

Regarding foreign policy issues, Young said in the interview:

He has a basic philosophical difference with the Carter administration policy that has halted progress toward normalization of relations with Vietnam. Young said he believes it is in the U.S. interest to establish communications with every nation, and that lack of communication contributed to the Vietnam War and its expansion into Cambodia.

The decision to authorize the 7th Fleet to pick up Indochina refugees may well increase the exodus from the countries in that area. If the United States opens its doors to a million people from almost any area, including most of Western Europe, "you could find a million takers pretty easily," he said.

Cuban President Fidel Castro was "quite helpful" to the United States in putting through the Panama Canal treaties by speaking to Panamanian leader Omar Torrijos about the importance of the agreement and helping to "low-key" the rhetoric on the issue.

He disagrees with increased military budgets, except for their utility as "a face-saving say for the Republicans to vote for SALT." On another issue tied to the strategic arms limitation treaty, Young said he believes the MX missile will never be built because the House will kill it.