Lausanne, Switzerland — Syria has finally stepped among Lebanon's feuding warlords, proposing a new power-sharing accord, a tightened cease-fire, and a national-unity government. At time of writing, the draft accord had not yet been made public -a step which senior Lebanese sources said would need to await final assent from the rival Christian and Muslim political leaders gathered here since last Monday. And after increasingly bitter recriminations and invective that have marked the past few days of negotiation, last-minute hitches could not be ruled out.
Yet senior Lebanese sources said an accord did seem virtually sure - after energetic intervention by the Syrian ''observer'' at the conference, Vice-President Abdel Halim Khaddam. He has so far done more listening than talking.
The accord would formally be presented as the work of Lebanese President Amin Gemayel.
''But it is, of course, Khaddam's,'' said one official.
The sources said the draft would probably be proposed and formally adopted in a full session of the nine rival Lebanese leaders late March 19. If so, the conference would likely end today.
As described by conference sources, the accord would stop short of a perfectly detailed blueprint for Lebanese political reform - the Syrians' presumed original hope for the parley. ''It is not the accord,'' said a ranking Lebanese official. ''But it is an accord.''
It would include principles - ''headlines,'' said one official privately - of agreed changes in Lebanon's war-ruined 1943 arrangement for Christian-Muslim power-sharing. The effect would be to recognize a shift away from the Maronite Christians' traditional dominance to an increasingly assertive, and powerful, non-Christian majority. Yet the drift would be toward Christian-Muslim equalization, not outright dominance over the Maronites.
The sources said the accord would also include:
* An upgrading of the level of representation in an extant multicommunal ''security committee,'' in hopes of cementing a so-far shaky cease-fire on the ground.
* Formation of a new ''national-unity'' government, whose main task would be to implement the agreed political reform principles. The new cabinet would probably be announced only after the Lebanese rivals have returned to Beirut. But it was understood that a veteran Sunni Muslim moderate, Takieddine Solh, will likely be the new premier. Mr. Solh, an elderly and soft-spoken man who still wears the traditional tassled fez of decades past, has the virtue of being on good terms with almost all of Lebanon's rival politicos - and, crucially, is similarly acceptable to the Syrians.
If the accord indeed pans out, it would at least reverse a trend of increasingly vocal enmity among the Lebanese rivals here in the past three or four days. Back in Lebanon, a cease-fire pushed through by Mr. Khaddam much earlier in the conference has similarly been fraying.
The almost thunderous question being asked in the hallways of the posh Beau Rivage Hotel, where the conference is meeting, has been: ''When are the Syrians going to make themselves heard?''