Israel braced itself for another major confrontation with the United States today as U.S. Defense Secretary Caspar W. Weinberger's just-concluded Middle East swing reverberated through Prime Minister Menachem Begin's government and opposition.

As Israel's parliament prepared for a full-scale debate Monday on the effects of Weinberger's policy declarations on U.S.-Israeli relations, the Cabinet today grappled with the implications of the proposed U.S. sale of F16 fighters and Hawk mobile antiaircraft missiles to Jordan.

After a three-hour Cabinet discussion, a government spokesman, in a briefing with reporters, said that if Jordan is allowed to purchase the sophisticated weaponry, "it would create a new and most dangerous element in the Middle East."

The Cabinet secretary, Aryeh Naor, added, "We cannot sit in silence and see how one of our worst enemies is going to arm itself. We cannot and shall not sit in silence and watch how the military balance in the Middle East is going to be changed."

Naor echoed a warning by Foreign Minister Yitzhak Shamir Thursday that completion of the arms deal could lead to a confrontation with the Reagan administration similar to that over the sale of airborne warning and control systems (AWACS) aircraft to Saudi Arabia last year.

Israeli Army Chief of Staff Lt. Gen. Rafael Eitan, meanwhile, warned that Weinberger's proposed arms sales could transform Jordan into the "focal point of the eastern front against Israel," displacing Syria, which has been preoccupied with internal political conflicts.

"The danger exists that Jordan will become the unifying element of the eastern front," Eitan said in a speech in Natanya today.

Begin, who has been recuperating from a broken thigh, did not attend today's Cabinet session, which reportedly was dominated by a discussion of statements made by Weinberger during his Middle East tour. However, a government spokesman said the prime minister will lead another Cabinet debate on the issue after Israel receives "clarifications" of Weinberger's statements from Washington.

Weinberger's trip has been a source of consternation to the Begin government ever since it first became clear that the defense secretary had no intention of visiting Israel but appeared committed to cementing U.S. military ties to Arab countries.

Because U.S. Secretary of State Alexander M. Haig Jr. had recently made two visits to Israel in an effort to revive moribund Egyptian-Israeli negotiations on Palestinian autonomy in the West Bank and Gaza Strip, officials here overlooked the omission of Israel from Weinberger's itinerary.

But last week Israeli officials began to express astonishment at statements, attributed to a "senior official" aboard Weinberger's plane, to the effect that the Reagan administration is "getting tough with Israel" as a result of a policy shift in Washington.

The Israeli concerns were heightened by Weinberger's disclosure of the planned arms sale to Jordan and by apparently inaccurate press reports that the United States intended to "redirect" its policy in the Middle East away from Israel and toward moderate Arab nations.

The reaction has been tempered, to a degree, by uncertainty over whether Weinberger's comments reflect the views of President Reagan.

"All we are doing now is trying to react to press reports. Even assuming the reports are accurate, which we can't do, we won't know what they mean until we get the clarifications," an official Israeli source said today.

But the Weinberger statements continued to generate controversy across partisan lines, with the opposition Labor Party joining Begin's Likud coalition in demanding a parliament debate today.

Israel's former ambassador to the United States, Simcha Dinitz, a Labor Party member, called the proposed arms sales to Jordan "a very grave situation in front of us."

Dinitz warned of a "change in substance" in U.S.-Israeli relations, and said that Israelis must be wary of publicly stated objections to Weinberger's views expressed by other members of the Reagan administration. Such objections, he warned, could be "tactical ploys" intended to placate Israel until completion of the withdrawal of Israeli forces from the Sinai Peninsula April 25.

Dinitz said Israel should insist upon entering "frank negotiations" with the United States on a mutual strategy for dealing with the Arab-Israeli conflict.