Efforts to achieve a negotiated settlement of the Lebanon crisis are hung on the problem of getting Israel to cut back overflights of that country in exchange for U.S.-provided alternate means of gathering intelligence, diplomatic sources said yesterday.

They said a key sticking point is whether U.S. intelligence-gathering substitutes such as satellite reconnaissance will be accepted by Israel as adequately meeting its security needs for information about deployment of Syrian military units and Palestine Liberation Organization forces in Lebanon.

Resolution of that question is considered crucial to chances of working out an agreement between Israel and Syria to defense the crisis and restore the delicate balance that existed in Lebanon until late last month when the Syrians deployed antiaircraft missiles there after two Syrian helicopters were downed by Israeli jets.

U.S. officials, keenly sensitive to the delicate negotiations being conducted through the Mideast shuttle effort of special U.S. envoy Phillip C. Habib, have refused to discuss specifics or identify the principal problems.

But, the sources said, both Syria and the Lebanese and central government apparently are inclined to accept the agreement if Syria's demands about the Israeli overflights are met. The sources added that Israel still has not committed itself on this point and that discussions continue on the various intelligence-gathering options the United States might provide.

To that end, the sources continued, Habib was instructed yesterday to continue his mission at least until Monday. Those instructions could change, since his progress is being reassessed on a day-to-day basis, the sources said. But the current plan is to have him continue through the weekend in hopes a break can be achieved.

U.S. officials, aware that the plan being hammered out by Habib is still in a tentative and fragile state, yesterday continued to resist efforts to characterize his proposals as "an American plan." In a lengthy go-around with reporters, State Department spokesman Dean Fischer repeatedly turned aside such references with the rejoinder: "We've said consistently that there is no such thing as an American plan."

Despite this reticence, reports from the Middle East quoting Israeli and other sources have described the Habib proposal as tentatively containing these elements:

Disengagement of Syrian peacekeeping forces and Christian militias that have been fighting each other in mountain areas northeast of Beirut.

An end to Syrian bombardment or the Christian city of Zahle, which dominates the strategic Beirut-Damascus road, with Lebanese army units taking over policing of the city.

An end to Israeli overflights of eastern Lebanon, with a tacit understanding that Israel would not be restricted from continuing operational flights against PLO guerrillas in southern Lebanon.

A staged withdrawal at a still unspecified time of the Syrian surface-to-air missiles in Lebanon.

Resumption by Saudi Arabia of financial support for the Syrian force, which was sent to Lebanon in 1976 under an Arab League peacekeeping mandate. w

A U.S. attempt to negotiate with Syria and Israel another "red line" agreement, or tacit understanding about specified zones of operation, similar to the one tacitly accepted by the two countries in 1976.

In a related Mideast development yesterday, U.S. officials characterized as "premature" reports from Cairo that agreement has been reached between the United States, Egypt and Israel on a multinational peacekeeping force to police the Sinai desert after Israeli forces withdraw under the Camp David agreements.

However, the officials said agreement appears to be near and that they expert the force to be ready for positioning in March, when the Israeli are scheduled to withdraw. The officials added that the force is expected to have from 2,000 to 2,500 men and that up to 1,000 will be American.