President Carter's announced determination to tie future warplane sales to Israel to sales of advanced aircraft to Saudi Arabia and Egypt has set off an unprecedented test of strength for the so-called Israeli lobby in Congress.

Carter's "package deal" of aircraft sales appears to be one result of the new diplomatic atmosphere produced by Anwar Sadat's peace initiative. Israel and its friends don't like that atmosphere, just as they don't like the proposed deal.

They have already begun a campaign to block the package in Congress. But administration officials insist that Carter will not abandon the plan - or his desire to demonstrate American "evenhandedness" in dealing with Arabs and Israelis.

Some administration lobbyists calculate that this is an issue on which the Israeli lobby can be beaten, though such a defeat would be unprecedented. They reason that the public and Congress have a new appreciation for the need to deal positively with Arabs as well as Israel.

The Ford administration took on the Israeli lobby in a comparable fight. In 1975 Secretary of State Henry Kissinger called for a "reassessment" of Mideast policy, and delayed arms shipments to Israel. This mobilized Israel's friends in Congress, and led to a statement of support for the Jewish state signed by 76 of the 100 senators.

Many members of House and Senate as well as key staff assistants on Capitol Hill said in interviews that Sadat's peace initiative may have changed the atmosphere somewhat, but they challenged the pregnosis that Carter can beat Israel and its friends in a showdown on the package deal.

The administration's package would include 60 F15 fighter bombers for Saudi Arabia, 50 F5E jet interceptors for Egypt and a combination of 15 F15 and 75 F16 fighters to Israel.

The administration has announced its plan to send formal notification to Congress - as required by law - of its intention to make these sales on April 3. If either the House or Senate passes a resolution of disapproval within 30 legislative days, any element in the package could be blocked.

This week Rep. Lester L. Wolff (D.N.Y.) says he will ask colleagues to sign a resolution urging the White House to put off all these arms sales in light of the delicate Mideast peace negotiations now under way. Wolff calls this the best way to avoid embarrassment both to the president and to the three countries involved.

Sen. Henry M. Jackson (D-Wash.) has made a similar proposal, and interviews with numerous members of both chambers and aides last week suggest that Congress would welcome a postponement of the entire issue.

But if the administration proceeds, a real donnybrook seems inevitable. Carter and his associates are expected to argue that the president must redeem his personal pledges to Saudi Arabia and Egyptian President Anwar Sadat or the United States will forfeit its status as an effective middleman and friend of both sides in the Middle East. Friends of Israel are expected to counter that the package deal amounts to renunciation of formal commitments to Israel and a threat to future Israeli security as well.

American Jewish activists appear deeply concerned that the Carter administration is tilting toward the Arab side, and Israeli officials speak of a threat to the historic "special relationship" between Israel and the United States.

These fears were reinforced at a previous unreported White House meeting on Feb. 23, when Zbigniew Brzezinski, Carter's national security adviser, dismayed or alarmed an influential group of Jewish leaders by criticizing Israeli government policy.

According to an administration associate who was in the room. Brzezinski made "a brutal, brutal attack, emphasizing to the assembled Jewish leaders that U.S. and Israeli interests and policies do not always coincide at the present stage of the uncertain peace negotiations.

That meeting was attended by Jewish community leaders from all over the country, officials of the Council of Jewish Federations and Welfare Funds and the American Jewish Congress. Jerold C. Hoffberger, chairman of the Baltimore Orioles and president of the council, said those present seemed to share a dismay about the tone and content of Brzezinski's remarks.

(A spokesman for Brzezinski said he was trying to take a long-term and broad view of both U.S. and Israeli interests in his remarks on Feb. 23 by arguing that both countries should support a moderate evolution in the Mideast rather than do anything to encourage radical trends there. "He certainly didn't consider it to be a brutal analysis," the spokesman said.

Uneasiness about the administration's course plus the opposition of the Israeli government to the package deal and their own concern about Israeli security have mobilized Jewish groups in the so-called "Israeli Lobby," and they are preparing a concerted assault on the package deal.

One administration official who has been following this embryonic confrontation predicted that Jewish groups will stage "a full-court press" on House and Senate members during the forthcoming Easter recess.

Other Jewish activists spoke more moderately, but all agreed that the Israeli lobby will fight hard to block the package deal.

Several Jewish organizations have already issued statements opposing the package, among them the influential Conference of Presidents of Major Jewish organizations led by Rabbi Alexander Schindler.

The White House argument is that the traditional bloc of pro-Israeli votes will not reappear in Congress on this issue. Several congressional sources described subtle changes in the mood of Congress - or at least of some members - as a result of the fluid and unpredictable situation in the Middle East since Sadat's trip to Jerusalem.

Many of Israel's oldest and most reliable friends in Congress - Sen. Abraham Ribicoff (D-Conn.), for example - have kept silent on this issue thus far. Some say privately that they are deeply troubled by the bargaining posture of Prime Minister Menachem Begin, and by the insistent and demanding position of the Israeli lobby here. (Other friends of Israel in Congress like Rep. Sidney Yates (D-Ill.) continue to support Begin and his government strongly, in private as well as in public.)

Seven of Jewish activists recognized the different climate but said there was no choice but to fight the package deal. "We could not let the Egyptians be rewarded for breaking off the peace talks," one said. Like many of the Jewish activists interviewed for this article, this source asked not to be named.

More substantially, they recalled the United States had made formal, written commitments to Israel in 1975 to supply the planes that have now been part of a package deal with sales to Israel's potential enemies. They called this a dangerous change in the historic American-israeli relationship as well as a betral of principle by the united States.

Some members of the House and Senate privately said they resented the pressures being applied on them by the Israeli lobby. One Senate aide complained that his boss was told that his vote on the F15 sale to Saudi Arabia would be a "litmus test" of his support for Israel.

A key aide in the House said that members appreciate the delicate issues involved in the package, which is why many hope to avoid the need to cast a vote on it.

In a speech on the Senate floor Thursday, Sen. Frank Church (D-Idaho), ranking member of the Foreign Realtions Committee, listed concisely for his colleagues the apparently unresolvable conflicts of American interests in deciding how to satidfy the Israelis, Saudis and Egyptians at the same time. "A very difficult issue," Church called it, without suggesting where he will eventually come down.

"Opponents of the package deal are expected to concentrate on the F15 sale to Saudi Arabia. The F15 is America's most sophisticated fighter airplane, and Israel argues that giving it to the Saudis would significantly aldle East. Rep. Woff, for example, said he woul giving it to the Saudis Wolff, for example, said he would press for disapproval of the F15 sale if the administration tries to press ahead with the package.

Moreover, Israel's supporters argue, by providing Saudi Arabia with a weapon that could be used - at least theoretically - againat Israel, the United States is ensuring that Saudi Arabia will become involved in any future Mideast war. Israel would have to preempt by taking out those F15s, it is argued, and that would mean an attack on the western world's principal supplier of oil.

If either chamber votes against the F15 sale, the administration will have to decide if it will stick to its threat to withhold the entire package, including the jets for Egypt and Israel. Secretary of State Cyrus R. Vance, among others, has said this would happen.

Rep. Benjamin S. Rosenthal (D-N.Y.) predicted that, in that eventuality, irresistible political pressure would build to sell Israel the planes it needs. Rosenthal and many others noted that the Israeli sale should have a special status, since it was promised in writing after the Sinai accords in 1975.

A showdown of this kind could provoke a spilt between Carter and the politically active Jewish community of enduring significance in American presidential politics.

But any attempt to predict the outcome of this contest appears premature on Capitol Hill. "It's very much up in the air," as Rep. Dante B. Fascell (D-Fla.) put it. (Fascell opposes the Saudi sale.)

An administration official said formal notification of the three sales might be postponed a few weeks if it appears that the Panama Canal treaties debate will get in the way of orderly Senate consideration of the issue. Otherwise, the notification will go up to the Hill on April 3, making a compromise or a showdown inevitable by early May, since Congress has 30 days to act.

Many sources noted that much could happen before then in the ever-changing Mideast. One occasion for possible unforeseen developments is Prime Minister Begin's impending visit to the United States, scheduled to begin March 13.