Israel determined to redeploy troops in Lebanon, but may modify timing

Despite the deteriorating situation in Lebanon, Israel wants to go ahead with the partial pullback of its forces there. This is what Israeli Foreign Minister Yitzhak Shamir and Defense Minister Moshe Arens will be telling President Ronald Reagan and senior United States officials. The two ministers are in Washington in place of Prime Minister Menachem Begin, who canceled his scheduled trip at the last minute.

Both Israeli ministers stressed before leaving that they did not expect the US to press Israel to postpone its redeployment. The Israeli news media have speculated that such US pressure will be generated by the fear that an Israeli troop pullback might spark domestic chaos in Lebanon which could undermine the American-backed government of Lebanese President Amin Gemayel. Analysts in Israel think this is the reason behind Mr. Reagan's invitation on Sunday for the Israeli ministers to visit Washington.

Despite the official hard line, there seems to be a modest potential for some Israeli flexibility on the timing of redeployment. ''. . . our friends in the United States know what the government of Israel has decided,'' said Foreign Minister Shamir before his departure, ''and we will stick to this decision.'' When asked whether Israel might delay its timetable for redeployment, Mr. Shamir said, ''I don't think so. I think that what may be expected is cooperation in the implementation of this decision.''

Although no official timetable has been set for the Israeli pullback, military and government sources have made clear that Israeli troops intend to be dug in along the Awali River 45 kilometers north of the Israeli border before winter sets in. To achieve this goal, sources here say the redeployment would have to begin in earnest by August.

While the US appears reluctantly to have accepted the Israeli decision to redeploy, the question of Israeli timing and coordination with both the US and Lebanon is crucial to all three parties. This will be a basic subject of the Washington discussions, according to sources here. But the sources insist that the final decision on timing will be made by the Israelis.

The Israeli decision to pull back, taken last week, is based on their conclusion that Syria will continue to block formal implementation of the Israel-Lebanon accord on Israeli troop withdrawal from Lebanon by keeping Syrian troops in that country. This opinion has not been altered by the appointment of Deputy National Security Adviser Robert C. McFarlane to succeed retiring special Middle East envoy Philip C. Habib, who was considered too pro-Arab by top Israeli officials.

The US fears that if Israel pulls back too soon, the newly rebuilt Lebanese Army may not be ready to take over the areas Israel leaves. Additional troops of the four--nation multinational peace-keeping force, which includes US Marines, would have to be sent into these areas. The key area of contention is the mountainous Shouf region where Lebanese Christians and fighters from the Druze Islamic sect are already battling for position in anticipation of the Israeli pullout. President Gemayel's position has been further weakened by the announcement, during his just-completed trip to Washington, of a challenge to his authority by three pro-Syrian Lebanese leaders, including Druze leader Walid Jumblatt.

The Israelis deny they will leave the Shouf precipitously, creating a vacuum into which Syrians or Palestinian fighters might infiltrate or which could explode into civil war.