As the realities of the concessions Israel is likely to have to make for peace become apparent, indications appeared today that wave of popularity Prime Menahem Begin has been riding may be starting to crest.

Former Prime Minister Yishak Rabin, a member of the Labor Party opposition, said he was "worried" about the autonomy Begin has outlined for the occupied West Bank because the creation of any entity that is not linked with neighbouring Jordan could lead to creation of a Palestian state "that will serve as a source of trouble."

Goulah Iohen, a member of Parliament from Begin's Herut faction, sadi Begin's "remarks on home rule mean a (Palestinian) national home. I never dreamed that he could utter such a sentence." Most other membrs of Herut are said to continue to support their leader, or at least to be willing to wait fot his explanations after he returns from abroad Tuesday evening.

Part of the piqu, including that among members of Begin's Cabinet who refuse to be named, is because the country's political leaders have been kept in the dark over Begin's thinking.

There is resentment that President Carter and Egyptian President Anwar Sadat, U.S. congressional leaders and even the American public are hearing first from Begin. Once he briefs his government Wednesday before going on to meet Sadat, that mood seems likely to pass.

The opposition newspaper Davar editotialized:

"Mr.Begin is probably anxious at this point to prevent critism from those who would say he was either too intransigent or too inflexible. But not for long can the public put up with such secrecy."

The latest poll, done for the London Sunday Times, showed that 76 per cent of the population trust the prime minister to make a good deal with Sadat and only 11 per cent distrust Begin. The poll was taken before his statements yesterday about what he plans to offer Sadat, however.

There is a growing sense of betrayal among some of Begin's most militant supporters in the Gush Emunim movement, the group that regards settlement in and retention of the occupied territories of the West Bank as a sacred right and duty.

To get Foreign Minister Moshe Dayan and the Democratic Movement for Change, the left-wing component or the conservative governing coalition, to join the goverment, Begin's Likud bloc has to pledge not to exercise Israeli sovereignty over the West Bank while negotiations were going on.

Gush Emunim has good reason to worry. A poll published by the newspaper Sadat's visit to Israel, public support for new Jewish settlements on the West Bank has mosedived from 68 per cent to 52 per cent. While highly vocal, the "Gush", as they known there, are thought to represent a tiny proportion of the vote.

Despite today's criticism and the risk that Begin will now start losing some ground in the polls, he is widely regarded as having no adversaries on his right significant enough to prevent his making the peace moves he sees fit.

He has so far taken care to stress that any agreement would have to include the right for Jews to continue to settle on the West Bank. Veteran Israeli observers say, however, that they doubt more than a handful of people would want to exercise that right once the area is returned to local administration.

The most notable shift is Begin's personal position so far has been the suggestion that the West Bank would bot be linked with Israel. The prime minister's statements in the United States also drpooed Foreign Minister Dayan's previous personal view that the area should be likned with Jordan.

Otherwise, the borders see no radical departures from previous Israeli government thinking in Begin's statements so far, only differences in degree.

As one analyst out is: "We're not going to allow the creation of an Arafat state on the West Bank," a reference to Yasser Arafat leader of the palestine Liberation Organization.

Diplomats here say that the West Bank population is not being offered anyting it does not already have. While mayors - pleaded to back the PLO - took over most townhalls in elections 18 months ago, diplomats say the indications they get that a maximum of 20 per cent of the West Bank population consists of hardcord "rejectionistss" who want no deal with Israel.

At gathering this evening in Arab East Jerusalem, one pro-PLO mayor, the American-educated Mohammed Hassan Mulhim of Haloul, a town near Hebron, argued that the PLO could hardly be called negative since it has not yet been offered anything by Israel to reject.

Mulhim spoke to reporters before attending a meeting of notables that endorsed a procalimation rejecting Sadat's peace moves and Begin's proposals and protesting any plan that falls short of independent statehood.

"Our people should be given the right of self-determination, the right to have a state without being under the patronage of anyone," the mayor said.

The meeting in East Jerusalem was labeled a "seminar on current events" to get around the Israel military administration's ban on unauthorized political gatherings. At least two other majors and a number of labor leaders attended, showing the depth of feeling on the West Bank. They have not recently dared to try to circumvent the Israelis that way.

Independent foreign analysts dismiss the current spate of delegations going grom the West Bank to Cairo to pledge their support to Sadat as being largely made of personalities with a history of doing the bidding of Israel and Jordan authorities.

But a large middle group is taken await-and-see position. The analysts say that most West Bani mayors admitted privately that public opinion is avoratable to Sadat and that the people hope his move will bring an end the Israel occupation.

Israeli officials won privately that they wae worried by the eupioria gripping their countrymen as emodied in such things as the 10,000 young people who gathered in Tel Aviv last night to hear an outdoor "song of peace" festival of Ibrew and Arabic songs and a suggestion by the chief of the Israeli negotiating team that Tel Aviv and Alexandria become sister cities.

Dayan is said to be cautioning privately that such phiro is drawing Israel along too st in a negotiating process that is bond to slow down, at the risk of disappointing public opinion. The details of the negotiations can be expected drag things out for months, Dayan reportedly is telling his colleagues.

The independent newspaper Masriv complained editially that by outlining his peace on the American television program "Face the Nation" yesterday, Begin was "facing the wrong nation."

"He didn't remember to take care of his people at home. He's running a one-man show," said an Israel woman.