The United States is making intensive efforts to arrange a United Nations peacekeeping force for southern Lebanon before the start of White House talks with Israeli leaders next Tuesday, informed officials said yesterday.

According to the sources, the Carter administration's current top Middle East goal is to get a peacekeeping agreement setting the stage for withdrawal of Israeli forces from Lebanon before the arrival here of Prime Minister Menachem Begin.

Otherwise, administration officials fear, the White House talks next week will bog down in discussion of the Lebanon problem - with little or no chance for a breakthrough on the more basic problems of a comprehensive Arab-Israeli peace.

Preliminary soundings with U.N. Secretary General Kurt Waldheim and foreign governments were described as sufficiently encouraging to allow the start of detailed planning for an international force in Lebanon.

If no hitches develop, the sources said, the U.N. Security Council, which began meeting on the Lebanon situation late yesterday, could vote creation of the peacekeeping force by Monday.

Initially, the force probably would be made up about 3,000 armed personnel with instructions to shoot if fired upon, the sources added. The first troops would probably come from Scandinavian nations and from units borrowed from the seven-national United Nations Emergency Force, which has patrolled the Sinai line between Egypt and Israel since the 1973 Middle East war.

Consideration also is being given to including a Lebanese military contingent in the new U.N. force. Since the area to be policed is Lebanese territory, the cooperation of the Beirut government would be very important to the operations of a peacekeeping body.

Some of the current diplomatic discussions are based on the premise that the U.N. troops would police all of southern Lehanon up to the Litani River rather than be confined to the six-mile border belt that Israeli forces have occupied as a security zone.

Israel has been unenthusiastic in the past about a U.N. role in southern Lebanon, fearing that such international units would ineffective against well-armed Palestinian commandos.

But U.S. officials argue that now is the time to reach a quick and extensive international agreement for the Lebanese border area. Otherwise, they reportedly have warned Israel, the Arab states, backed by the Soviet Union and nonaliged nations, are likely to ram through a U.N. resolution condemning the Israeli invasion and occupations.

In testimony yesterday before the Senate Foreign Relations Committee, Harold H. Saunders, who has been designated the new assistant secretary of state for Middle Eastern affairs, hinted strongly that Israel is close to agreeing to the peace force plan.

Saunders said he thought Israel's concern could be resolved if the peacemaking troops are given "a mandate to control access to the area" and "show the capacity to exert that control" in the face of efforts by Palestinian commandos to move back into southern Lebanon.

Saunders and Alfred B. Atherton Jr. the administration's special roving envoy for the Middle East peace talks, also testified before the committee in closed session. Reliable sources said they conceded that despite the administration's hopes for a quick peacekeeping agreement, certain pitfalls still needed to be avoided.

Chief among the difficulties, they reportedly said, is the need to secure the agreement of Israel and Lebanon, which have not yet formally committed themselver to a peacekeeping force, and of those other countries with a close involvement in the Middle East conflict.

Reports from Cairo yesterday quoted Foreign Minister Mohammed Ibrahim Kamel as saying that Eygpt does not object to a U.N. force, provided it has Lebanon's approval.

Less clear was the attitude of Syria, which has 30,000 troops in Lebanon, and of Syria's backer, the Soviet Union, , which could use its Security Council veto torpedo the plan.

However some sources said they believed Syria will give the plan its approval because the substitution of a U.N. force would remove the danger of a confrontation between Syrian and Israeli troops within Lebanon. Moscow, the sources, added, would almost certainly be guided by Syria's wishes.

As to Israel the sources said, Washington privately has told the Begin government that Israeli forces should be withdrawn from Leanon, whether the U.N. force is created or not. However, it was not clear whether that was a position with which Washington will stick or a pressure tactic aimed at pushing Israel into acceptance of the peacemaking force.

In a related development, several members of the Foreign Relations Commitee told Atherton and Saunders that the administration must be much more forceful in informing Saudi Arabia that the United States disapproves of the financial support it gives the Palentine Liberation Organization.

Otherwise, the Senators warned, the administration could find a stiffening of congressional opposition to its planning Middle East package of plane sales to Saudi Arabia, Egypt and Israel. The administration argues that Saudi Arabia should be included in the package because it is a moderating force among the Arab countries. U.N. troops be stationed along the Isreali-Lebanese border.

Yet uncompleted negotiation with Syria, other Arab's countries as well as the Soviet Union and the United States apparently explained his vagueness.

Butros spoke to reporters after a meeting with Syrian Foreign Minister Abdel Kalim Khaddam who said his country's decision about a U.N. force would be made known at the Security Council meeting.

Syria's attitude was considered crucial for Lebanon since Syrians dominate the 30,000-man Arab Peacekeeping force here.

In the past, Syria and the other Arab countries have rejected similar proposals on the grounds that they would bind the hands of the Palentinian guerillas in their fight against Israel. But analysts suggested that Syria might reluctantly agree to less a U.N. force as a lesser evil out of fear that rejection could suck the Damascus government into a war with Israel.

The viability of the American plan was also dependent on the Soviet attitude. If Lebanon wants the buffer force, the Kremlin would have no trouble backing the proposal since it has recently begun championing Lebanon's sovereignty and territorial integrity.

But the Soviets also want to maintain influence with the Palestinians whose spokemen yesterday said they would ask for a Soviet veto of the U.S. proposal at the U.S. proposal at the Security Council.