Israel this week said it will ''reassess'' its participation in talks aimed at ending the Israeli occupation of south Lebanon if a partial military agreement is not reached with the Lebanese within 10 days.
The Israeli insistence that it must reach some agreement with Lebanon by Dec. 20 was a clear effort to pressure both the Lebanese and the Syrians to speed up the talks that began just over one month ago.
The Israelis have asked Richard Murphy, undersecretary of state for Near East and African affairs, to pass their message along to both the Lebanese and Syrian governments, Israeli officials said.
''Those who are dragging their feet in the talks are the Lebanese themselves, '' a spokesman for the Israeli Foreign Ministry said Monday. ''The point is that the Lebanese are not interested in reaching an agreement since they are not in a hurry for us to leave,'' said the official, who spoke on condition he not be named.
If that assessment is true, Israel's only ability to pressure either the Lebanese or the Syrians lies in the implied threat of a unilateral withdrawal of Israeli troops.
Some 15,000 Israeli troops have occupied the south, up to the Awali River, since Israel invaded Lebanon 21/2 years ago.
Some Lebanese officials fear that a sudden Israeli pullout would create a power vacuum in the south that could lead to factional bloodshed.
The Israelis made public their carefully worded threat to ''look at our options'' as Israeli and Lebanese Army officers met for their ninth round of talks in Naqurah, under the auspices of the United Nations.
Since the talks started last month, each side has accused the other of impeding progress.
The immediate sticking point, however, is Israeli insistence that UNIFIL troops - the UN forces that have patrolled parts of south Lebanon since the Israeli invasion in 1976 - be deployed to patrol areas that Israel evacuates.
It is on the role of UNIFIL that the Israelis have said they want to reach agreement with the Lebanese by Dec. 20.
The Lebanese have insisted that the only troops who should take the place of the Israelis are members of the regular Lebanese Army. The Israelis claim that the Lebanese Army is too weak to provide the security for Israel's northern border which the Israelis say they must have before agreeing to withdraw.
Israel points to the Lebanese government's failure to deploy its troops down a 21-mile stretch of the coast highway from Beirut to south Lebanon as evidence of government and Army weakness.
The deployment, designed to extend the government's control beyond Beirut, has been opposed by Druze leader and Lebanese Cabinet minister Walid Jumblatt. Mr. Jumblatt has said the planned deployment would threaten Druse strongholds in the Shouf mountains.
Syria is thought to be pressuring Jumblatt to allow the scheduled deployment to take place.
The Israelis have long thought the Syrians to be the key to reaching an agreement with the Lebanese on any Israeli withdrawal from the south. The Syrians maintain a force in eastern Lebanon's Bekaa Valley, and Syrian officials regularly summon members of the Lebanese Cabinet to Damascus for consultations.
''The talks would not have been held at all without Syrian agreement,'' said the Israeli Foreign Ministry official. ''But we have not seen Syrian activity to put pressure on the Lebanese negotiating party to reach an agreement with us.''
The Israelis have sought, through American mediation, an informal guarantee from the Syrians that they will help ensure Israel's security. Syrian President Hafez Assad, however, has been unwilling to give such a guarantee.
Mr. Murphy, as well as UN envoys, has made several trips to Damascus, seeking some sort of ''gentlemen's agreement.'' But some diplomatic sources said that the Syrians may be in no hurry to see an end to the Israeli occupation, which has cost the Israelis in lives, expenditures, and morale.
Israel's latest threat to reconsider its participation in the talks in Naqurah, south Lebanon, came just after an agreement was reached to recess the talks from Dec. 20 to Jan. 8.
''We don't see a point in going into a New Year's vacation without reaching any results until the eighth of January,'' the Israeli Foreign Ministry official said. ''We want to have some achievement before this date.''
Israel's dilemma is that its only alternatives to continuing the talks are a unilateral withdrawal or a partial redeployment of its forces out of the populated areas of the south.
A partial redeployment would get Israeli troops out of hotspots such as Tyre and Sidon and probably reduce Israeli casualties. But it would not end the expense of the occupation, or satisfy a growing desire by the Israeli public to end the unpopular involvement in Lebanon.
A full withdrawal runs the risk of exposing Israel's northern settlements to guerrilla attacks - and this time, such attacks might come from indigenous Lebanese Shiite Muslims, not from the Palestinians that Israel drove from the south during the 1982 invasion.
Some Israeli officials fear that the occupation has created such hatred toward Israel among southern Shiites that they will not be appeased by the withdrawal of Israeli troops to the international border.
Because the alternatives are so unsatisfactory, Israel probably will remain in the Naqurah talks for the time being. It is clear, however, that Israeli officials hope the latest threat to leave the talks will produce some sort of breakthrough soon.