Despite strong political opposition, President Reagan has decided to go ahead with the sale to Saudi Arabia of a controversial military aircraft package including highly sophisticated AWACS radar reconnaissance planes, the administration announced yesterday.

But, well-informed sources said, in an effort to avert a costly and emotional political fight that could result in Congress' blocking the sale, the administration will postpone, probably until sometime this summer, submitting the package for congressional action.

According to the sources, the timing on sending the plan to Congress still has not been decided and will require careful consultation with congressional leaders.

These include Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), who has just completed a visit to Saudi Arabia and other Mideast countries, among them Israel, which strongly opposes the AWACS sale as a threat to its security.

However, the sources added, the administration is unlikely to push the issue in Congress, where there are now signs of strong reservations about the AWACS part of the package, until after the Israeli national election scheduled June 30.

At that time, the sources said, the administration hopes that emotions generated by the issue will have cooled and that it will be better able to placate Israel's congressional supporters by assuring them that various safeguards are in place against AWACS being used in ways harmful to Israeli defense interests.

The package, which has large-scale diplomatic and political implications for the administration, includes five AWACS planes and equipment to improve the offensive capability of 62 F15 jet fighters, whose sale to Saudi Arabia had been approved earlier.

The F15 enhancements involve range-extending fuel tanks, air-to-air missiles and airborne refueling tankers.

Successful completion of the deal is considered critical to the administration's desire for continued close relations with Saudi Arabia, which is this country's major supplier of crude oil and also looms large in Secretary of State Alexander M. Haig Jr.'s high-priority hopes of creating a force to counter Soviet pressure in the strategically important Persian Gulf region.

Originally, the Israelis agreed grudgingly to offer only pro forma opposition to the F15 aspect of the deal.

After the administration decided on March 6 to add the AWACS planes to the package, the Israelis vowed to make an all-out fight to block that sale, contending that such planes would give the Saudis the ability to collect vital intelligence data about Israeli defenses and pass it to Israel's enemies in the Arab world.

Congress can halt the sale if both House and Senate vote against it by a simple majority within 30 days after formal administration notification of intent to sell the equipment.

Administration officials concede that they failed to sound out congressional sentiment before a decision at a National Security Council meeting April 1, two days before Haig left on a Mideast tour, to move ahead with the congressional notification shortly after Congress reconvenes next week.

While Haig was in the Middle East, the administration belatedly became aware that congressional sentiment, even in the Republican-controlled Senate, was running so strongly against the AWACS part of the package that the deal was in serious danger of rejection.

Republican leaders warned Reagan that even if the package was salvaged, it would be at the cost of a bruising battle that could cause the president to expend much of the credit he needs to get his economic program through Congress.

That triggered a barrage of recent speculation that the administration was considering splitting the AWACS from the package for later consideration. Haig helped fuel this speculation when he mentioned to reporters last Friday that he had told the Saudis in Riyadh two weeks ago that keeping the AWACS planes in the package could jeopardize the entire arrangement.

However, sources familiar with those discussions said that Haig, while giving the Saudis that warning, also reassured them of the administration's intention to send the full package to Congress.

On the other side, the Saudis, while continuing to insist on the AWACS sale, are understood to have indicated they will not object to a delay in pushing ahead -- provided it does not drag on for more than two or three months.

The Saudis will require a large number of U.S. specialists to help them operate the planes, and the administration, as part of its effort to reassure Israel's supporters, is expected to use that as a wedge to negotiate an arrangement that will give the United States a measure of control over any AWACS intelligence and prevent its improper distribution.

Because of Saudi sensibilities, that will require some difficult negotiation, and much of the burden is likely to fall to Robert Neumann, whom Reagan nominated Monday to be U.S. ambassador to Saudi Arabia.

Neumann, 65, headed the Reagan transition team at the State Department and previously served as ambassador to Afghanistan and Morocco.