Israeli Prime Minister Menachem Begin's rightist opposition in parliament is sending a "truth squad" to shadow Begin and Egyptian President Anwar Sadat during their talks next month in Washington and to attempt to obtain a commitment from presidential candidates to support Israel.

The conservative Knesset (parliament) members are convinced that with the approach of the election the time to wring concessions from the United States is running out. They are fearful that Israel will face difficulties once a president is elected and the U.S. Jewish vote is not needed for another four years.

They will demand a freeze on the implementation of the Egyptian-Israeli peace treaty and a complete review of the accords before the last third of the Sinai Peninsula is returned to Egypt in March 1982.

Led by members of the Tehiya (Renaissance) Party and the ultranationalist Gush Emunim (Faith Bloc) settlement movement, the so-called truth squad plans to meet with presidential candidates and their staffs and to launch an extensive media campaign designed to encourage the candidates to make far-reaching commitments to Israel to which they will later be held accountable.

The group already has enlisted the support of ultranationalist American Jewish organizations, including Americans For a Safe Israel, U.S. Gush Emunim backers and former members of Begin's Herut Party who have become disenchanted with the prime minister's policies in Israel.

In addition to exerting pressure on presidential candidates, the squad hopes to create the appearance of intense domestic political pressure on Begin in Israel, thereby providing the prime minister leverage with which to resist new negotiating demands by Egypt and the United States.

"We have to do it now, before the elections. All Israelis know what it is like the first year after an American election," said Knesset member Geula Cohen, one of the organizers of the squad.

She was referring to a common Israeli perception of American politics, in which campaigning presidential candidates are seen appearing before well-heeled American Jewish organizations wearing yarmulkes and pledging absolute commitment to Israel's well-being. The same candidates, according to the stereotype of the more cynical of the Israelis, usually kick off their campaign with a trip abroad to the "three Is" -- Israel, Italy and Ireland.

But Israel has come to anticipate hard times in the aftermath of the sweeping promises, and sometimes they point out it is no accident that the detested Rogers Plan was adopted as American policy in 1969, an inaugural year in Washington.

Named after then-secretary of state William P. Rogers, the plan evolved out of Soviet-American negotiations and envisioned a binding peace agreement in which Israel would withdraw to the 1967 borders, except for "insubstantial" boundary alterations. It remains a symbol in Israel of United States attempts to impose a settlement in the Middle East at the expense of Israel's security.

Cohen, who broke away from Begin's ruling Likud coalition over the Camp David accords and who was ejected from the Knesset March 12, 1979, for interrupting President Carter's speech there, said the purpose of the "truth squad" trip was to prevent a recurrence of such a "betrayal."

She will be joined on the cross-country campaign by Knesset member Moshe Shamir, also of Tehiya Party; Yuval Neeman, former president of Tel Aviv University and now Tehiya chairman; and Rabbi Eliezer Waldman, head of the yeshiva at the Kiryat Arba settlement near Hebron in the West Bank. The group will be in the United States from April 9-26.

Gush Emunim and similar ultranationalist movements in Israel are more than fringe groups, largely because of their alliance with and influence upon the major sectarian faction in the Knesset, the National Religious Party. That party, with 12 Knesset members, is the pivotal partner in Begin's shaky Likud coalition and its defection would bring down the government.

The Tehiya Party, a splinter from the Likud, has only two members in the 120-member Knesset, but a number of the Herut (Freedom) Party members who are in the Likud share Tehiya's views and, from time to time, threaten to leave the coalition.

Shamir and Cohen, in an interview, argued that the time had come to take Egypt out of the autonomy negotiating process and put a freeze on Israel's withdrawal from the Sinai while the accords are reviewed.

"We don't want to abolish the treaty. We believe peace with Egypt is possible. But when it comes to Judea and Samaria [the biblical names for the West Bank], we believe Israel should make a fresh start without Egypt," Shamir said.

He called Israel's autonomy scheme a "disastrous plan which will inevitably lead to a Palestinian state and the possible destruction of Israel." As a result of Camp David, Shamir said, "Israel accepted the role of a criminal holding stolen property."

Recalling the origins of the 1948 War of Independence, and the 1967 Six-Day War, when Egypt led the Arab attacks on Israel, Shamir said, "Our gains in those wars were justified and legitimate. What Begin has done now, by making Egypt a partner in negotiations, is the most shattering departure from the basis of Israel's justification. By making Egypt a partner, we surrendered to Egypt whatever claims we had on those territories." p

Shamir and Cohen said their "truth squad" would also advocate the immediate annexation of the occupied Syrian Golan Heights, which they claimed is supported by 71 Knesset members but which has never been submitted to a vote for reasons of political expediency.