The question of how to get foreign troops out of Lebanon goes to Washington this week.
And central to this is Israel's demand for an adequate military buffer zone on its northern border.
Top United States officials will look over proposals being carried by visiting Israeli Foreign Minister Yitzhak Shamir Oct. 14. Then, on Oct. 19, Lebanon's new President, Amin Gemayel, is scheduled to meet President Reagan and other American officials.
The Israeli plan calls for a 25- to 35-mile security zone above Israel's northern border, policed by Lebanese Army soldiers, not by international peacekeeping forces, and free of heavy artillery. It demands this guarantee before its troops are withdrawn.
The sticking points: Israel will insist on a key role in the security zone for Maj. Saad Haddad, leader of the Israeli-backed Lebanese militia forces along Israel's border. Major Haddad's continued role is opposed by both the Lebanese government and the United States as a hindrance to the reestablishment of a strong central authority in Beirut.
Israel also wants a written security agreement from the Lebanese government pledging that Lebanese territory will not again be used as a base for hostile activities. The Israelis will also request some kind of joint Israeli-Lebanese commission to supervise implementation of the security arrangements.
Both items would be viewed here as important signs of normalized Israeli-Lebanese relations in lieu of a peace treaty, which Israel still desires but has decided to play down for now.
Following his meeting Thursday with US Secretary of State George Shulz, Mr. Shamir is scheduled on Friday to see Vice-President George Bush and, according to reports from Washington, Defense Secretary Caspar W. Weinberger.
Shamir will be discussing a timetable for withdrawal of foreign forces from Lebanon, which now seems less of a problem than it originally appeared. Israel at first insisted that Palestine Liberation Organization (PLO) troops, estimated at from 6,500 to 10,000, leave east and north Lebanon before an estimated 30,000 Syrians and 70,000 Israelis quit the country. But Foreign Minister Shamir indicated in a recent US television appearance that prior PLO withdrawal was not mandatory, thus leaving the way open for an American proposal of staged simultaneous withdrawal by all forces.
Israel will insist that its soldiers taken prisoner, its missing men, and bodies of its fallen soldiers be handed back by Syria and the PLO before any evacuation.
But sources here expect Israeli ideas on security arrangements and on the US role in negotiating them may not jibe with American conceptions. Defense Minister Ariel Sharon has publicly accused the US of actively seeking to prevent Israel and Lebanon from reaching a peace treaty and of trying to reduce direct contact between Israeli and Lebanese officials. He insisted the US should reduce its role in the negotiations.
Israel's foreign minister, on the other hand, reportedly is more sensitive to the delicate political position of Lebanon President Gemayel within the Arab world.
President Gemayel, in expected meetings with Mr. Reagan, will make known Lebanon's economic ties with the Arab states. He also will likely express his interest in a ''special relationship'' with neighboring Syria that could result in some form of mutual defense pact.
Lebanese Prime Minister Shafik Wazzan recently said Lebanon would be ''the last Arab state'' to sign a peace treaty with Israel. Lebanese officials do not disguise their eagerness for the US to play a major role in negotiating a foreign troop withdrawal.
Informed sources here say Israel's possibilities for a peace treaty will improve once foreign forces have left Lebanon and President Gemayel has reestablished central authority. This view has apparently triumphed as Cabinet Secretary Dan Meridor has said officially that a peace treaty is ''not a condition'' for an Israeli pullback.
Differences are likely to arise between the US and Lebanon, on the one hand, and Israel, over continued Israeli backing of Major Haddad. Prime Minister Menachem Begin is said to feel a strong sense of personal loyalty to the major. On the other hand, President Gemayel's late brother, the assassinated President-elect Bashir Gemayel, had said he would like to court-martial the renegade major.
Questions may also arise about the extent of Israel's desired security zone, formerly set at 40 kilometers (25 miles) but now put by Israeli sources at 50 to 55 kilometers (almost 30 miles). Israeli military officers have told correspondents it is because Syrian 180-mm cannons, which normally have a range of 42 kilometers, could hit targets up to 50 to 52 kilometers away if placed in the Lebanese mountains. But some experts here note that this weapon is very old and doubt it could obtain such range.