More than at any time since he was elected in 1977, Prime Minister Menachem Begin is facing an imminent collapse of his fragile parliiamentary coalition and the prospect of an election before the end of his term.

The end of Begin's rightist Likud government -- beset by triple-digit inflation and constant ministerial squabbling -- could come as soon as next week. And, according to a timetable that was being circulated widely in the Knesset, or parliament, today, a national election for a new parliament and prime minister would be held on May 17, six months earlier than scheduled. a

The opposition Labor Party is preparing a motion to dissolve the Knesset on Tuesday, on the basis of charges that the government's ability to function has disintegrated. Barring an 11th-hour shift of alliances, it appears that Begin's opponents could muster enough votes to defeat the coalition.

Labor leader Shimon Peres, anticipating a coalition crisis and an opportunity to put his party back in power, has postponed a visit to the United States to be on hand for the showdown.

However, Begin's often repeated success in surviving coalition crises when it appeared his government was doomed has tempered somewhat the expectations within the opposition. Begin has withstood dozens of no-confidence votes in the knesset during his stormy rule -- most recently Nov. 19 with only three votes to spare -- and nobody was ruling out the possibility that he would patch up the coalition one more time.

On paper, the Likud government has enough of a margin to barely withstand a Labor Party challenge. The coalition can count on 61 votes of the Knesset's 120 members, and possibly more if one or more of several tiny splinter factions swings to support the government.

But separate threats of resignations made this week by Finance Minister Yigael Hurvitz and Education Minister Zevelun Hammer over a controversial teachers' wage increase proposal have jeopardized up to 12 votes in Begin's coalition. If either of the ministers quit and took with him party allies in the Knesset, Begin's government would certainly collapse.

The immediate issue is a special study commission's recommendation to increase teacher salaries 30 to 60 percent, while also improving teacher training and making other reforms.

Hurvitz, who last year was promoted to deputy prime minister and charged by the Cabinet with rescuing Israel's deteriorating economy with stringent anti-inflationary measures, has repeatedly said the teacher wage hikes will cause labor bargaining chaos throughout the country and that he would resign if they are approved.

On Sunday, in the heat of a Cabinet debate on the issue, he hastily scrawled a resignation note and passed it to Begin, but later withdrew it in hopes of reaching a compromise.

For his part, Hammer, who promised Israel's public school teachers he would win them the raises, has vowed to resign if the study commission's recommendations are not adpopted by the cabinet.

The National Religious Party, to which Hammer belongs, has indicated that its 12 Likud coalition partners in the Knesset would leave the government if the education minister resigns, thereby assuring a collapse of the coalition. But it is also certain that if Hurvitz quits the Cabinet, his three-man Rafi faction will vote against Begin and assure the Likud's fall from power.

As it stands now, before resolution of the Hurvitz-Hammer impasse, Begin can count on the following 61 votes in the Likud coalition to support him in a no-confidence vote: his own Herut Party, 20; the Liberal Party, 12; the Laam faction, four; the Rafi faction, three; the Democratic Movement, three; the orthodox Agudat Yisrael Party, four; the National Religious Party, 12, and one-man factions, three votes.

The Labor alignment, on paper, can count on 29 votes from Peres' Labor Party, five from the leftist Mapam faction, five from the communist parties, six from the Shinui faction, two from the dovish, Shelli Party, two from the ultranationalist Tehyia Party, and four from independents, including former Likud foreign minister Moshe Dayan and former defense minister Ezer Weizman.

The six swing votes come from the three-man Ahva Party, with which Begin flirted briefly and unsuccessfully for a possible alliance to save his majority, and three independents.

The prime minister has been meeting with Hurvitz and Hammer in a desperate effort to find a compromise, but Cabinet sources said that none appears in sight. If a solution is not found by Sunday, they said, then Begin may submit his resignation before the Knesset can dissolve itself. In that case, under Israeli law, President Yitzhak Navone would appoint the current Cabinet as a caretaker government and new elections would be scheduled anyway.