Secretary of State Cyrus Vance ended a round of inconclusive conferences with moderate Arab leaders yesterday and postponed for one day a visit to Damascus at the request of President Hafez Assad of Syria, a leader of the militant Arab bloc.

Following a working luncheon with Saudi Defense Minister Prince Sultan, the last of his scheduled meetings here, Vance expressed satisfaction that he had answered pressing and important questions put to him about the Camp David agreements here and in Jordan. But he was given no assurance in either place that his answers had transformed initial opposition into support for the U.S.-sponsored peace arrangements.

According to the familiar, "senior American official" who often travels with secretaries of state and speaks to reporters on condition that his name and high post not be reported, Vance hopes for a decision from King Hussein about taking part in the Camp David arrangements by the time the Jordanian monarch comes to the United States next month. There is no timetable for a new Saudi statement, the senior official said.

The crucial role of Hussein and the mounting pressures on him from all sides were dramatized by a surprise visit to the Jordanian monarch east of Amman yesterday from Palestine Liberation Organization chief Yasser Arafat and Libyan leader Muammar Qaddafi, both of whom have bitterly denounced the Camp David accords.

Arafat and Qaddafi have been attending a conference of militant Arabs in Damascus, and their surprise trip across the border to Jordan evidently figured in the temporary postponement from today to Sunday of Vance's appearance in the Syrian capital.

Syrian President Assad, in accepting a U.S. bid for talks with Vance on the Camp David accords, had scheduled the meeting with the secretary of state for today, just after his hardline guests from Libya, Algeria, Southern Yemen and the PLO were expected to leave Damascus.

When the conference of militants proceeded more slowly than planned - evidently due in part to the sudden meeting with Hussein - Vance was asked to delay his trip. Late yesterday he agreed to cool his heels in Saudi Arabia for another 24 hours to accomodate Assad, whom he now plans to see in Damascus about noon tomorrow.

Vance plans to spend the extra day in a sightseeing trip to the oilfield center at Dharan.

It was something of a surprise to some officials that the Syrian leader had agreed to a visit from Vance at all under the circumstances. Several months ago Assad refused a visit from U.S. Middle East negotiator Alfred Atherton, because Atherton was engaged in negotiations between Egypt and Israel which he disapproved.

There were indications that the Saudi leadership had played a role in suggesting to Assad that he meet Vance on the current trip. The $90 million U.S. aid program for Syria, which was recently cut from an appropriations bill by the House and retained in the Senate only at Vance's urging, may also have been a factor in Assad's decision.

In a meeting with reporters yesterday at the Saudi guest palace where Vance is staying, the "senior American official" reported that the controversy with Israel Prime Minister Menachem Begin over a freeze on Jewish settlements on the West Bank had made Vance's mission to Arab states "more difficult."

The official said, however, "I'm quite confident" that the U.S. position on the settlements freeze will be sustained "because I know what was agreed to" at Camp David.

According to an informed account by officials traveling with the secretary, President Carter and Vance reached agreement on the settlements issue with Begin, Israeli Foreign Minister Moshe Dayan, Defense Minister Ezer Weizman and legal counsel Aaron Barak in a Camp David meeting last Saturday night. The agreement, according to the U.S. side, was that no new Jewish settlements would be established while the planned West Bank administrative councils are being set up and thereafter such settlements will be subject to agreement - and this a veto - by the negotiating parties for the West Bank, Israel, Egypt, Jordan and the Palestinian councils.

The first indication of trouble, according to this account, came on Monday when Israel transmitted its version of the letter to be exchanged among the parties on this issue. The letter committed Israel to freeze West Bank settlements for only short period.

U.S. officials reportedly took the matter up with Begin Monday night, and Carter included a statement of the commitment as he understood it in his address to a joint meeting of Congress. Begin said then, according to the officials, that he would have to withhold an authoritative reply on the question until he had returned to Israel and consulated his Camp David negotiating team, which had already left for home.

The "senior American official" said yesterday he believes that Begin will agree with the American version of the commitment once the Israeli leader discusses the matter with his colleagues in Jerusalem.

On another of the controversial statements Begin has been making, the senior official backed the Israeli premier. Asked if it were true that the United States at Camp David agreed to back Israeli demands that its troops remain in West Bank garrisons after the five year "transitional" period, the official replied, "If it appeared it was necessary, the answer is yes, we would."

Another U.S. official who participated in the meetings said both the United States and Egypt had agreed that Israel has a "good case" for stationing its troops on the West Bank idefinitely for security reasons. The final decision, according to the Camp David accords, would be up for negotiation among the various parties concerned with the West Bank.