Persistent sniping kept tensions high in this ravaged city yesterday as envoys from the six countries that contribute to Lebanon's peacekeeping forces convened at a 19th-century emir's palace to discuss proposals for ending the conflict between Syrian troops and rightist Christian militias.

The Beirut press billed the conference, at Beit Eddine in the rocky hills 25 miles southwest of the capital, as crucial in determining whether Lebanon has a chance to halt the violence that has ripped it apart in the last 3 1/2 years.

But Western political observers here said the most the Arab diplomats could hope to achieve would be consolidation of the current cease-fire that has stopped the heavy shelling since Oct. 8.

Even some of the participants seemed to be playing down the importance of the gathering, called by Lebanese President Elias Sarkis to endorse his new "security plan" for Beirut and the rest of the country.

The conference was scheduled to begin yesterday morning in the 150-year-old hillside palace of Emir Bashir II. But the opening session was delayed about seven hours because only the Qatari delegation showed up on time. Moreover, Qatar and Sundan sent ambassadors instead of the foreign ministers requested by Sarkis.

The last to appear at the palace, were delegations from Saudi Arabia, Kuwait and Syria. Syria Foreign Minister Abdul Halim Khaddam blamed his late arrival on the rain. But other sources said he and his Persian Gulf colleagues had delayed to meet in Damascus with President Hafez Assad of Syria.

Lebanese Defense and Foreign Minister Fuad Boutros told reporters the delegates were unanimous in a commitment to end the conflict peacefully. But after two rounds of talks, the only agreement announced was one to meet again today.

Both the Syrians and Christian militia leaders made public statements on the eve of the conference reaffirming tveir stands, which at face value would seem to doom Sarkis' proposal to replace Syrian forces in key Beirut districts with handpicked units of the fledgling Lebanese army and enlarged contingents from other Arab countries.

Right-wing Christian political leader Camille Chamoun and the top militia commander. Beshir GGemayel, demanded complete withdrawal of all Arab troops, including the Syrians, and their eplacementy by a U.N. force.

Referring to reported proposals for more Saudi troops and possibly Jordanians to replace Syrian forces, Chamoun said, "We cannot tolerate additional troops from any Arab country."

Syria, for its part, said the only solution to the conflict was to "liquidate the Israeli-backed militias." Damascus has also vetoed proposals by Sarkis in the past to withdraw some of its men in favor of Lebanese army regulars.

A joint Moslem-Christian unit of about 500 Lebanese soldiers took up security duties in the militia-controlled but Syrian-surrounded Christian suburb of Hadath on Friday. But there was no confirmation of reports that Syrians would cede their strongholds in other shell-battered Christian districts to Lebanese troops.

Syria supplies over 90 per cent of the more than 30,000 man Arab Deterrent Force, whose Arab League mandate as Lebanon's peacekeepers expires Oct. 26.

Saudi Arabia, the force's main financial backer, provides a 1,500-man contingent along with small units from the United Arab Emirates and Sudan. Qatar and Kuwait contribute to the $180 million annual budget but supply no troops.

Sudan has indicated a desire to pull its troops out when the current mandate expires. The Sudanese have announced no reason for their decision but are known to be close to Egypt, which is locked in a dispute with Syria over the Camp David accord and President Anwar Sadat's dealings with Israel.