Syrian involvement in Secretary of State George Shultz's efforts to achieve an agreement on Lebanon may ease the way toward an accord on the withdrawal of foreign forces from this fractured country, according to Lebanese officials.
Lebanese Foreign Minister Elie Salem briefed Syrian President Hafez Assad May 2 on Lebanese President Amin Gemayal's weekend talks with Mr. Shultz.
Mr. Salem is also reported to have reassured Syria that Lebanon will not bow to Israeli demands for a continued security presence in south Lebanon.
The foreign minister's visit to Damascus is the first publicized official contact between Lebanon and Syria in two months. Earlier Mr. Salem said that any agreement between Lebanon and Israel will have to be endorsed by Syria.
Officials in Beirut hope that Mr. Salem will return to the Lebanese capital with a sense of what Syria's intentions are. Syria has repeatedly said that it will only withdraw its forces from Lebanon once all Israeli troops have left the country.
But during the past week Syria's official press has severely attacked Mr. Shultz's visit to the Middle East. US flags were burned during May 1 demonstrations in the Syrian capital.
Many Lebanese blame Syria for this weekend's firing of rockets at US Ambassador Robert Dillon's residence in the hills above Beirut, where Mr. Shultz was spending the night.
Recent visitors to Damascus say, moreover, that public opinion in Syria is being geared up for yet another military clash with Israel. Reports from the Bekaa Valley in east Lebanon speak of the reinforcement of Syrian positions.
But Lebanon is banking its hopes on President Assad's invitation to Mr. Shultz to visit Damascus later this week. US officials told reporters that Syria had suggested several possible dates for a Damascus visit by the secretary.
Officials and analysts in the Lebanese capital say the involvement of Syria in the negotiating process may avert a failure of Mr. Shultz's mission in the Middle East.
Syria, according to well-informed sources, is the main stumbling block for an agreement between Lebanon and Israel. Last month President Gemayal sent Prime Minister Shafik Wazzan to Riyadh, Saudi Arabia for talks with King Fahd in the hope that Saudi Arabia may pressure Syria to soften its hard line. But Mr. Wazzan returned to Beirut with only vague Saudi pledges of support.
Analysts in Beirut say that Syria is building up the tension in the Bekaa Valley as a demonstration that it cannot be ignored.
''President Assad is making the same mistake Egyptian President Nasser made in June 1967,'' said a prominent Lebanese columnist. ''Nasser pushed the situation to the brink of war, convinced that the United States could control Israel, but he miscalculated. Assad is now doing the same thing again.''
For Syria a lot is at stake in Lebanon, according to senior Arab diplomats. Syria, these diplomats say, will lose some of its leverage over the Palestine Liberation Organization once all foreign forces have been withdrawn from Lebanon. A Lebanon withdrawal agreement may enhance US credibility in the region and weaken radical Palestinian opposition to an accord between PLO chief Yasser Arafat and King Hussein of Jordan.
Mr. Arafat, now in Damascus, is reported to have sent a letter to King Hussein this weekend. Earlier the Jordanian monarch told the Lebanese daily an-Nahar that he will not enter the peace process without PLO endorsement and that he is ready to resume his talks with Mr. Arafat.
Negotiations between Jordan and the PLO broke down last month following radical Palestinian and Syrian opposition to a draft agreement drawn up by King Hussein and Mr. Arafat which would have allowed Jordan to enter peace negotiations on the basis of President Reagan's proposals.
Faced with Syria's hard line and Israeli intransigence, President Gemayal is increasingly being forced into a position where he may have to choose between the continued occupation of large portions of Lebanese territory and acceptance of an agreement that will likely be rejected by large segments of the Arab world.
''President Gemayal will have to take a personal political decision,'' said one well-informed source, comparing Mr. Gemayal with the late Egyptian President Anwar Sadat on the eve of the Camp David accords. ''For the first time in Lebanese history our President may be forced to take a Lebanese rather than an Arab decision - a decision which could cost him his life.''
Said a source familiar with the negotiations: ''It's a Greek tragedy. Only a change in the Syrian position can avoid a bitter end.''