Underlying tension between President Carter and Israeli Prime Minister Menachem Begin, simmering off and on ever since the start of the Camp David summit, is heating up again under the latest threat to the Israeli-Egyptian peace treaty.

The immediate issue today is the deadlock between Israel and Egypt over President Anwar Sadat's demands for a target date to conclude follow-up negotiations for self-rule on the West Bank and in Gaza. The deadlock has thrown the administration's mediation effort into jeopardy and the way it came about has, fairly or not, further undermined U.S. confience in Begin.

The target-date formula for Gaza and the West Bank was hammered out the night of Nov. 11 in nearly four hours of tough bargaining between Secretary of State Cyrus Vance and the chief Israeli negotiators: Foreign Minister Moshe Dayan, Defense Minister Ezer Weizman and Aharon Barak, the Israeli legal expert. It has no binding effect and it would not be included in either the preamble of the treaty or the treaty itself but in a side letter.

But when that Dec. 30, 1979, target-date formula was presented to Begin at Kennedy International Airport in New York the next day, the prime minister rebuked his negotiators in front of Vance for having agreed to it.

This was a virtual repeat of an earlier Israeli performance when Begin's cabinet rejected "linkage" between the Egyptian-Israeli treaty and the follow-on West Bank-Gaza issues agreed to by Begin's negotiators as part of the treaty's preamble. American pressure reversed that rejection of a target date for automomy in Gaza and the West Bank.

At stake here is the heart of the Camp David compromise that President Carter believed inextricably "linked" Israel's peace treaty with Egypt to follow-on negotiations on the West Bank and Gaza. One American Mideast insider told us that the Israeli "contortions" to undermine the linkage understanding reached at Camp David were similar to Begin's backing out of his agreement with Carter on the question of Jewish settlements on the West Bank. Carter was not amused.

What particularly angers Carter's men is the repeated Israeli charge that the United States is doing Egypt's work at Israel's expense - tilting toward Sadat. Even Dayan, perceived here along with Weizman as an extremely able and resilient negotiator, said last week in Israel that "I don't think the Americans always use an equal yardstick toward us and toward Egypt."

Carter and his top aides disagree. Not a word or phrase in the once-disputed preamble to the treaty or in the still-deadlocked side letter on "linkage" makes the Israeli-Egyptian treaty conditional on what happens - or does not happen - on the West Bank or Gaza. U.S. mediators have repeatedly told the Israelis that Egypt has never attempted to impose a legal obstacle to carrying out any of the terms of the Israeli-Egyptian treaty because of what may happen on the West Bank.

Carter's impatience is growing. Moreover, the president and his men believe that if the deadlock over "linkage" persists, they hold most of the political cards to put serious pressure on Begin - pressure that so far has not been applied.

Top Mideast officials here, speaking around the country in public forums in support of Carter's peace efforts, report that Israel's overall political strength in the United States seems to be declining. Two questions from the audience have dominated those sessions: When will the United States "stand up" to Begin? Why must American taxpayers pay Israel some $3.5 billion - in addition to the regular $1.8 billion of routine, annual U.S. aid - for the Egyptian treaty?

A recent poll by the Roper organization strengthens the finding that American voters may be becoming more skeptical about Israel. Asked about the use of U.S. troops to protest access to Mideast oil, barely over half of Roper's respondents said they were opposed; but asked about U.S. troops if Israel needed help against an Arab invasion, 65 percent said they were opposed.

Carter insiders privately insist that at the lowest point of the Camp David summit, when all chance of compromise seemed gone, the president was pondering an exhaustive post-summit review that, however gently, would have isolated Israel. That fateful possibility evaporated when agreement was achieved at the last moment.

But Carter men say that presidential weapon, sheathed after the Camp David breakthrough, is still available. If the deadlock over "linkage" threatens to undermine the treaty, it could be unsheathed - and use with possibly telling effect.