Sen. Jesse Helms (R-N.C.), completing a turnabout in his position on Israel, led six other Republican senators yesterday in a concerted attack on President Reagan's September 1982 Middle East peace initiative and urged him to support continued Israeli occupation of the West Bank, Gaza Strip and Golan Heights.

They also asked him to "blunt Soviet expansionism" in the region by ruling out a Soviet role in any forthcoming peace talks.

At the same time, the senators called on the president to press Egyptian President Hosni Mubarak, who arrives here Saturday, to "honor his obligations to establish normal relations with Israel" through "practical steps."

The letter was signed by Sens. Helms, Steve Symms (R-Idaho), Mack Mattingly (R-Ga.), Chic Hecht (R-Nev.), Alfonse M. D'Amato (R-N.Y.), Paula Hawkins (R-Fla.) and John P. East (R-N.C.) and 12 House members.

Sent Wednesday to the White House, the letter made no mention of any specific steps Mubarak should take.

But a House resolution introduced by Reps. Ron Wyden (D-Ore) and John S. McCain III (R-Ariz.) and co-sponsored by 106 other members called on Egypt to return its ambassador to Tel Aviv, increase trade and tourism with Israel and curb alleged "anti-Semitic remarks" in the press.

Egypt withdrew its ambassador to Israel in September 1982 to protest the Israeli role in the massacre of Palestinians by Lebanese Christian militamen in the Sabra and Shatila refugee camps outside Beirut.

In their five-page letter, the Helms group took sharp issue with the underlying premise of Reagan's 1982 initiative, the exchange of Israeli-occupied Arab lands for Arab recognition of Israel. They asserted that the occupation was "not an issue at the core of the Israeli-Arab dispute" and that the Arab demand for Israeli withdrawal "may only be the prelude to the step-by-step dismantlement of Israel."

The concept of land for peace "is of grave concern to us," they said. "Israel cannot continue to be a strategic asset -- or even a viable nation -- if it is made strategically vulnerable."

"We need to strengthen our Israeli ally by helping her maintain strategic depth and deterrent capability," the letter said. "Strong assurances from the United States that Judea and Samaria will remain under Israel control will encourage the Arab inhabitants . . . to reach a modus vivendi with Israel and encourage Israel to give maximum local autonomy."

Judea and Samaria is the biblical name used by Israel when referring to the occupied West Bank.

The Helms letter represents a landmark in the conservative leader's changing views of Israel since the Israeli invasion of Lebanon in June 1982 and the massacres. He was sharply critical, calling for a halt to U.S. arms sales to Israel and saying it would be "beneficial" if then prime minister Menachem Begin resigned.

Close associates said the North Carolina senator, having fought a close reelection battle last fall with former governor James B. Hunt, who had strong support among Jews, has been shifting his views on Israel ever since.

They cited in particular the influence of Michael Kleiner, a former conservative Israeli Herut deputy, who was here last spring and spent long hours talking to Helms. In addition, a small pro-Israel group, Americans for a Safe Israel, appears to have played a role in changing Helms' mind.