SYRIANS PERSIST IN EFFORT TO END LEBANON'S CRISIS
High-ranking Syrian mediation mission appears determined to patch together durable truce among Lebanon's warring factions as edgy calm settles over Beirut on Sept 21; Syrian Foreign Min Abdel Halim Khaddam says 'we will not leave Lebanon until the crisis is solved'; some heavy-weapons fire is traded in southeastern suburbs of Beirut; Khaddam's mediation efforts come as Interior Min Camille Chamoun, repr in Cabinet of Maronite Christians, is reptd on verge of resigning in face of Premier Rashid Karami's unwillingness to call army into Beirut's guerrilla war; observers believe resignation will bring country to edge of civil war; Imam Moussa Sadr, head of Lebanon's Shiite Moslem community, after meeting with Syrian Pres Assad, says Assad believes civil strife in Lebanon is 'linked to developments in the Middle East' and threatened to 'overrun the regional equilibrium in favor of Israel'; it is believed in Lebanon that if country's factional fighting degenerates into civil war Syria will intervene militarily to restore order; Israel has issued warning to Syria not to intervene militarily; Khaddam confers with Karami, Chamoun, Pres Suleiman Franjieh and PLO leader Yasir Arafat; Karami says it was agreed to take necessary measures to stabilize cease-fire so that all efforts can be directed to natl reconciliation; leftists, led by Kamal Jumblat, insist that right-wing Phalangist party accept their program of 'progressive reforms' as basis of discussions; hope to alter Natl Covenant of '43, which gives leading pol role to Maronite Christian community and divides electoral offices on basis of religious affiliation; Phalangist leader Pierre Gemayel opposes altering Natl Covenant and has threatened to 'internationalize the crisis' if it is not solved soon (M)
