Saudi Arabian Foreign Minister Saud Faisal called on the United States yesterday to endorse Palestinian self-determination and begin dealing directly with the Palestine Liberation Organization to create conditions for a negotiated settlement of the conflict in Lebanon.

Saud's statement came as he and Syrian Foreign Minister Abdal Halim Khaddam held preliminary talks at the State Department before today's much-heralded White House meeting at which an official Arab request for Israeli withdrawal is to be presented to President Reagan.

U.S. officials have expressed hope that the visit of the two foreign ministers can lead to a breakthrough in the stalled Beirut negotiations over a future home for 5,000 to 6,000 trapped PLO fighters.

But a two-hour meeting late yesterday of the emissaries and Secretary of State George P. Shultz ended with no clear sign of movement on any issue.

Saud said he was convinced of the "good intentions and motivations" of the United States but announced no conclusion about U.S. policy. Khaddam said he had asked the United States to assume its responsibility as "a country that is extending a huge military, political and economic assistance to Israel to put an end to Israeli aggression." He would not elabaorate.

Washington Post correspondent William Branigin reported from Beirut that former Lebanese prime minister Saeb Salam, a key mediator in the talks there, said today's meetings here will be vital not only for the Beirut negotiations but for the future political direction of the Arab world.

From Jerusalem, Washington Post correspondent David B. Ottaway reported that Israeli officials said new military action against the trapped Palestinians would become more likely if the Washington talks fail to indicate progress toward a breakthrough in the Beirut negotiations.

There was no immediate indication of Reagan administration willingness to shift its Palestinian policies in line with the Saudi requests, which Saud said have also been transmitted in recent diplomatic traffic from Riyadh to Washington.

Before Saud disclosed his position to reporters and took it to the meeting with Shultz, a State Department spokesman said the longstanding U.S. position against contacts with the PLO has not changed.

Spokesman Dean Fischer said Khalid Hassan, a senior member of the PLO governing legislature, the Palestine National Council, will not be permitted to join meetings with U.S. officials unless the administration determines that the PLO has met the seven-year-old U.S. demand that it accept Israel's right to exist and U.N. Security Council resolutions 242 and 338.

Hassan, who is in Washington, is not part of the official Arab delegation that is to meet Reagan today, according to Clovis Maksoud, the Arab League's ambassador here.

Saud, in a 40-minute meeting in early afternoon with several reporters, rejected the commonly held belief that Arab nations are the cause of the current impasse in Beirut because they have been unable to decide which countries will take the PLO fighters.

Saud said the PLO has agreed in principle to leave Beirut and that Iraq and Algeria, among others, have made known a willingness to accept the guerrillas on an interim basis. He expressed confidence that other temporary refuges for them can be found.

The basic problem, as he portrayed it, is that the Palestinians need assurances from the United States and the international community about their "ultimate destination." In this respect, he said, the Arab world is unified in believing that they should be permitted to return to Palestine, specifically the occupied West Bank and Gaza, to determine their own future.

Such assurances, Saud said, are "an absolutely necessity" for the Palestinians, who "must know where they are going" in the long run.

For the United States to accept the principle of self-determination for the Palestinians and to undertake contacts with the PLO, Saud continued, would be "encouraging elements" that could lead to success in the current negotiations and lay groundwork for a general settlement of the Palestinian problem.

Israeli Prime Minister Menachem Begin's government has been strongly opposed to anything resembling "self-determination" for the Palestinians, on the belief that this would lead to an independent Palestinian state on the West Bank, threatening Israeli security.

Shultz, in confirmation hearings before the Senate Foreign Relations Committee last week, declared that "the legitimate needs and problems of the Palestinian people must be addressed and resolved--urgently and in all their dimensions." But there is no clear signal of how Shultz and the administration will proceed.

Saud, in his meeting with reporters, also called for U.S. guarantees to the Arab world that U.S. arms and aid provided to Israel will not be "misused" to destroy the rights of others, which he charged has been done in Lebanon under a claim of Israeli security.

Senate Foreign Relations Committee Chairman Charles H. Percy (R-Ill.), following a closed meeting of his committee with Saud, said "the Arab world would hold us responsible" if Israel attacks West Beirut with U.S. weapons. Percy said Saud had indicated that, in such a case, some unspecified Arab retaliation would be likely.

Giving his own view that this might be withdrawal of Arab money from U.S. banks, a cutback in oil production and/or increased solidarity of the Organization of Petroleum Exporting Countries, Percy said, "We face one of the most critical periods this country has faced since World War II."

Saud did not mention the possibility of retaliation in his talk with reporters. He expressed antipathy to the Israeli position, saying it is "at least ironic" that Israel is the party expressing urgency about its encirclement of Beirut and declaring that "most probably" Israel will ask the United States to pay for the invasion.

In Jerusalem, an Israeli official quoted by Ottaway said he did not think it correct to speak of "days" in estimating the timing of a possible Israeli assault on the trapped guerrillas if today's meeting fails to produce results. But the official refused to say how much longer Israel might wait.

Former Lebanese prime minister Salam, in an interview with Branigin in Beirut, said the United States can put the Middle East on the path of peace if it can avert an Israeli assault on West Beirut.

"Now the radicals are at an ebb, and moderation is dominant everywhere in the Arab world," he said. "Will America let this opportunity slip? Because it really is the last one." He predicted a resurgence of Palestinian terrorism if a political solution fails.