The Reagan administration, arguing that Saudi Arabia's ability to defend Persian Gulf oil supplies must be strengthened because of the Iran-Iraq war, is planning a $1 billion arms sale to the Saudis including 1,600 Maverick antitank missiles whose sale was withdrawn in June because of congressional opposition.

Sources familiar with the plan said yesterday that the administration is expected to notify Congress shortly after it returns from its summer recess on Sept. 9.

Congressional sources, noting that the proposed package also includes up to 14 of the latest F15 jet fighter planes and improvements to earlier-model F15s and other American weaponry already in Saudi stockpiles, predicted that the move will touch off a major new test of strength between the White House and the Democratic-controlled Congress.

These sources warned that the administration can expect pro-Israeli members and others disenchanted with Saudi Arabia to fight the plan with the same ferocity that forced the White House into its earlier retreat on the $360 million sale of Mavericks and that almost derailed another Saudi missile sale last year. In May 1986, President Reagan vetoed legislation blocking the sale of Sidewinder air-to-air, Harpoon air-to-sea and Stinger ground-to-air missiles, and he then had to fight to narrowly prevent Congress from overriding the veto.

Administration officials, while confirming details of the plan, denied that they were trying to gain "the advantage of surprise" by moving immediately after the recess. One senior official said the timing was dictated by the Persian Gulf situation and by the need for sufficient time for the required consultations with Congress before the end of its current session, which could come as early as October.

The same official also said there are "no surprises" in the proposed package because its components have been discussed in informal contacts with key members of Congress, leaders of American Jewish organizations and the Israeli government. He noted that Reagan, in withdrawing the Maverick sale proposal June 11, said the action was "only temporary." Until now, however, Reagan has not indicated when he would launch a new sale effort.

The senior official said the administration believes that Iran's increased threats, which led to U.S. escorts of reflagged Kuwaiti tankers, will strengthen Reagan's arguments that a militarily strong Saudi Arabia can be an effective deterrent to the Iranians and also might alleviate the need for further increases in U.S. forces.

But congressional opponents contended that recent events in the gulf have not significantly toned down the frustration and annoyance with Saudi Arabia on Capitol Hill, which stirred fierce opposition to the earlier missile sales. The hostility was rooted in perceptions that the Saudis maintain high oil prices at the expense of the West, that they have been a negative force in Middle East peace efforts and that they have not been as helpful as possible to U.S. military and diplomatic efforts in the gulf war.

The critics said these resentments have not been allayed by private administration assurances that the Saudis are cooperating closely in such areas as radar surveillance, but have to keep their efforts quiet because of domestic political problems and to avoid an open confrontation with Iran.

In June, Congress briefly was swept by a wave of especially intense anti-Saudi feeling following unconfirmed and subsequently denied reports that a Saudi F15 had refused to attack the Iraqi plane that seriously damaged the USS Stark in a missile attack last May.

In addition to the Mavericks, the most controversial part of the new package is likely to be the proposal to sell 12 to 14 of the latest-model F15s. The opponents charge the sale would be tantamount to providing the Saudis with an entire new squadron of planes valued at more than $500 million.

However, administration officials said the planes are intended as "attrition aircraft" that would keep the Saudi fleet of F15s at 60 planes by replacing aircraft that crash or wear out. The officials insisted that the administration believes it had an unwritten understanding at the time of earlier F15 sales that a cushion of replacement planes would be provided.

They acknowledged that 14 planes are far more than the Saudis presently require as replacements, but said it was necessary to buy that number now because F15 manufacture will be phased out next year. The plan, they said, is to keep most of the planes in this country and send them to Saudi Arabia only as they are needed as replacements.

Opponents of the sale said the administration also plans to sell the Saudis an unspecified number of Bradley Fighting Vehicles. But administration officials said the sale of the Bradleys took place earlier and that the Saudis later decided that they would rather buy the vehicles from Pentagon stocks rather than from the manufacturer. Under the law, the officials said, that change means that the sale must be resubmitted to Congress in the same manner as a new sale.

The Saudis also would be allowed to buy a variety of electronic equipment to give their older-model F15s better flight and combat capabilities, improved computers and gun barrels to upgrade 150 M60A1 tanks to the level of newer M60A3 models and a new type of ammunition feeder for the Saudis' M109 self-propelled artillery.