Arab League efforts to end Lebanon's latest outburst of violence appeared to founder tonight, dealing a potentially serious blow to American presidential envoy Philip C. Habib's mission to defuse the Middle East missile crisis.

Even before a two-day meeting at the presidential summer palace in this mountain town 25 miles southeast of Beirut ended today, Syrian and Christian militia gunners were exchanging artillery fire at Zahle in Lebanon's Bekaa Valley, close to the site of Syrian surface to air missile batteries that have aroused Israeli anger.

It was over the issue of security arangements at that eastern Christian town, under Syrian siege since April 2, that the talks stumbled, according to militia officials. The militias also rejected a key Syrian demand that they break off relations with their Israeli allies.

The Kuwaiti, Saudi Arabian, and Syrian foreign ministers meeting with Lebanese President Elias Sarkis under Arab League auspices left after issuing a communique that simply "recorded the commitment of all sides" to abide by a nationwide cease-fire.

Since the outbreak of violence here in April 1975, more than 60,000 Lebanese have been killed, about 750 of them in the present round of fighting. l

Other complicated proposals on the table here for ending the current crisis were deferred to another ministerial session to be held in Saudi Arabia June 23. In turn the Arab League committee said it would "complete its mission" here in a meeting July 4.

Despite the renewed shelling, militia officials said Saudi Arabia had promised to guarantee relative quiet on the ground until the June 23 meeting. The intervening period would be used to work out if and how the militias might cut their controversial ties with Israel and how Lebanese troops might be added to the now totally Syrian peacekeeping force as the militias have requested. The 22,000-man Arab Deterrent Force has tried since 1976 to police Lebanon under an Arab League mandate.

Earlier, militia officials privately described the two-day meeting as a "failure."

"We do not despair," one said, "there will be a second meeting, but that does not mean there will not be a second failure."

Asked about the future of the Habib mission, which had placed great hopes in Saudi Arabia's ability to bring about a reconciliation between the Christian militias and Syria, the officials said, "Who still remembers, who thinks about Habib?"

[Habib left Paris today on his way to the Midde East for another round of shuttle negotiations, The Associated Press reported. U.S. officials declined to give his destination, but Arab reports said he was going first to Saudi Arabia.]

Habib had hoped to use Saudi leverage to bring about a disengagement in Lebanon and thus defuse the crisis between Syrian and Israel.

That crisis developed April 28 when Israel aircraft shot down two Syrian helicopters and Syrian replied the next day by moving in SA6 surface-to-air missiles. Israel has threatened to destroy the missiles unless Syria removes them.

Other Arab League proposals presented at the meetings here were, according to informed sources:

De facto Syrian control of the eastern Bekaa Valley, which Syria considers its soft underbelly vulnerable to attack from Israel and its Christian Lebanese allies.

The provision that Palestinian guerillas would be allowed to operate in in southern Lebanon under reworked terms of the outdated 1969 Cairo accords, but that deterent force units, including Lebanese Army troops, would be stationed in the now Palestinian-controlled southern ports of Tyre and Sidon.

The final blow to the proceedings was delivered in a three-hour evening session yesterday at the presidential palace above Beirut to Baabda between overall militia commander Bechir Gemayel and the Saudi and Kuwaiti ambassadors.

Gemayel, underlining his militant mood by appearing for the meeting in military uniform, rejected the demand that the militias' break with Israel thereby reducing the conference to an effort to work out immediate security measures rather than a long-term political solution for this divided nation.