The Reagan administration is planning to sell Jordan advanced arms worth up to $750 million, but agreed yesterday to postpone these sales temporarily in hopes that King Hussein's diplomatic initiatives will persuade Congress that he is serious about direct peace talks with Israel.

U.S. and congressional sources said the administration originally had intended to go ahead this week with plans for seeking $250 million in economic aid for Jordan as part of its supplemental appropriations request for this year.

However, the sources added, at a White House strategy meeting late yesterday a tentative decision was made to defer that request, which had been intended as a signal of U.S. support for Hussein's efforts to form a joint Jordanian-Palestinian delegation able to negotiate directly with Israel on a Middle East peace settlement.

The administration is said to be considering proposing arms sales that could total $750 million over a five-year period.

The weapons would include advanced U.S. fighter aircraft, either the F20 or the F16; mobile Hawk surface-to-air missiles; shoulder-fired Stinger antiaircraft missiles, and troop-carrying helicopters.

The sources said the agreement to put the controversial arms sales on hold for the present was worked out by Secretary of State George P. Shultz, Senate Majority Leader Robert J. Dole (R-Kan.) and Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.).

According to the sources, Dole and Lugar had warned that proceeding with the arms sales at this time would provoke bitter opposition from Israel's congressional supporters and result in a probable congressional veto of the sales that would undercut efforts to help Hussein.

The administration also was told that many of the 22 Republican senators facing reelection next year do not want to be put in the position of having to take a stand on the Jordan arms package without having a lot more evidence that Hussein's efforts are leading to direct talks with Israel.

Shultz has been seeking to convince a skeptical Congress that the Jordanian monarch's visit here two weeks ago represented a breakthrough in the peace process. But Shultz clearly needs more time to change the prevailing view in Congress that Jordan is not really serious.

Shultz and his aides have been citing numerous statements that Hussein made while here, including his readiness to engage in direct negotiations with Israel, albeit under the auspices of a U.N. Security Council-sponsored international peace conference.

Both the United States and Israel have rejected this formula because it would give the Soviet Union a role in the negotiations. But Shultz has accepted the idea that Jordan needs "broad international support" for any direct talks.

On Monday, Israeli Prime Minister Shimon Peres put forth his own five-point peace plan that called for an international conference within three months and "enlisting the support of the permanent members of the Security Council" for it.

The State Department did not comment yesterday on the specifics of the Peres plan. But it cited Peres' proposals as "yet another reflection of the momentum toward direct negotiations which is currently building in the region."

Sens. Edward M. Kennedy (D-Mass.) and John Heinz (R-Pa.) last week sponsored a nonbinding resolution, cosigned by 67 other senators, opposing sales of advanced weapons to Jordan while that country "continues to oppose the Camp David peace process and purchases arms from the Soviet Union."

Congressional sources said that a strenuous administration lobbying effort had failed to induce these senators to take their names off the resolution and had been instrumental in helping to convince Shultz that a lot more preparatory work has to be done to create a receptive atmosphere on Capitol Hill for a long-term U.S. security relationship with Jordan.

As a result, the sources continued, Shultz plans to begin by making public the comprehensive review undertaken by the State Department earlier this year of U.S. arms policy in the Middle East.

It is expected to make the point that Jordan faces security threats from Syria and other radical Mideast states, particularly if it moves toward peace with Israel, and requires advanced arms to create a credible deterrent force.

The study, which could be released as early as today, will reportedly say that if Jordan continues to be frustrated in its hopes of obtaining modern weapons from the United States, it is likely to turn to the Soviet Union. That would raise the danger of the king coming under Soviet influence and moving away from direct peace talks, the department will argue.

To help Shultz in making these points to the Senate, the sources said that Lugar had promised to hold a Foreign Relations Committee hearing on the Jordan arms question before Congress goes into its July 4 recess.

Then, the sources said, later this summer the administration and the leadership will reassess the situation to see whether the administration's lobbying and possible further progress by Hussein toward talks with Israel have created a more favorable climate for getting the sales through Congress.

The sources said the $250 million under consideration could be requested at the same time the Mideast arms review is sent to Congress.

The sources said $200 million would be in unrestricted funds that Hussein could use for a variety of uses and $50 million would be for specific projects. The administration's aid requests for Jordan for next year include $117 million in military assistance but no economic aid.