Arab leaders have told the United States the the Palestine Liberation Organization may change its position on Isreal, and top officials of the Carter administration yesterday sent out public signals of encouragement.

It was not clear whether the projected PLO shift would go far enough to meet U.S. requirements for the beginning of official contacts and a PLO place at a Geneva conference.

Secretary of State Cyrus Vance said through his spokesman that PLO acceptance of U.N. Security Council Resolution 242 would be sufficient to bring about the start of U.S. PLO discussions.

The resolution, adopted 10 years ago, affirms the right of Israel, and all other Middle East countries, "to live in peace within secure and recognized boundaries free from threats or acts of force."

Vance was informed here Sunday night by Saudi Arabian Foreign minister Saud al Faisal that the PLO has "a change in position coming" regarding Resolution 242, State Department spokesman Hodding Carter said. Other sources said similar reports had come from leaders in Syria, Jordan and Egypt.

"We do not have independent verification," the spokesman said. officials traveling with Vance said the United States had expressed interest and asked for further details from the PLO through intermediaries.

As relayed by U.S. officials, Saud's statement and those of other Arab leaders were not precise on the change that the PLO contemplates. APLO spokesman in Beirut, within hours of the American announcements, denied that an outright acceptance of Israel is planned.

[In Jerusalem, Israeli Prime Minister Menahem Begin refused comment on the American statement.]

In Plains.Ga., President Carter said "we don't know" whether the PLO will take the step of fully accepting the United Nations resolution, but if it does so, "that would open an avenue that they might participate in the Geneva conference."

"The thing that has made the Palestinians reluctant to do this was, at the time 242 was passed, it only referred to Palestinians as refugees," Carter said. "If the Palestinians should say "we recognize U.N. Resolution 242 in its eltirety but we think the Palestinians have additional status other than just refugees' that would suit us okay."

Carter said that with the Vance mission still in the Middle East "things look better than they did. I hope we can work somthing out on the Palestinians. That is the biggest obstacle right now."

PLO acceptance of Israel would be a historic reversal by an organization at war with the Jewish state through commando raids and other means. It could only be accomplished over the bitter objections of those within the umbrella organization who reject any coexistence with Israel, and probably would lead to a split.

Saudi Arabia and other major Arab countries are reported to have urged Palestinian leaders to accept Israel in the context of a regional settlement, in return for the creation of a Palestinian state of occupied land given up by the Jewish state. Arab leaders should take the first step of reconciliation, however.

In the past, the PLO has strongly objected to the wording of U.N. Resolution 242 for several reasons, among them the fact that the text makes no reference to Palestinians except as "refugees."

State Department officials said the United States will not agree to alter the wording of the resolution. President Carter said, however, that "it would suit us" if the PLO added to its acceptance of the resolution a statement asserting "additional status" for Palestinians.

The Central Council, the link between the PLO working leadership and the governing Palestine National Council, is scheduled to meet Aug. 16 in Damascus. There was speculation yesterday that a change in the stand toward Israel would be discussed and perhaps announced there.

Palestinian coexistence with Israel on a peaceful basis is considered by many to be essential in the long-run to a stable Arab-Israeli settlement. Thus PLO acceptance of Israel, if it does come, would be a shift of major significance.

In the short run, however, a PLO shift at this time could complicate U.S. relations with Israel and create additional uncertainty about a new Geneva conference.

Israel has bitterly opposed any dealings with the PLO. In September 1975, it extracted a secret written promise by then Secretary of State Henry Kissinger that the United States would not recognized or negotiate with PLO so long as that organization did not accept Israel's reights to exist and U.N. Resoulations 242 and 338.

While U.S. officials have been tempted to make contact with PLO, the Carter administration has said it is "constrained" by Kissinger's memorandum. Starting several weeks ago, Carter began saying that the United States will definitely deal with the PLO if the organization accepts Israel-something which the Kissinger memo implied but did not explicity state. Carter told Time magazine the United States would begin talks with the PLO "immediately" if its conditions were met, a comment that caused disquiet in Israel.

Another part of the Kissinger memorandum gives Israel effective veto power over the particpants at a Geneva conference.