The American Israel Public Affairs Committee, this country's principal pro-Israel lobby, has told the administration that it will not actively oppose President Reagan's proposed $354 million sale of advanced missiles to Saudi Arabia, AIPAC sources and administration officials said yesterday.

AIPAC's decision to take a "hands-off" position is expected to boost considerably the administration's campaign to counter efforts in Congress to block the sale. The AIPAC stance follows the lead of the Israeli government, which had indicated it would not mount a major campaign against the sale because it wants to avoid friction with the administration over an arms package that Israel does not consider a threat to its security.

Although AIPAC is expected to maintain a pro forma opposition to the Saudi deal, the sources said that Thomas A. Dine, AIPAC's executive director, told Secretary of State George P. Shultz on Thursday that his organization will not mobilize its lobbying apparatus behind legislation to oppose the sale.

In explaining the decision, AIPAC sources said they were motivated by a desire not to disturb good relations between Israel and the administration and by the fact that the arms package -- consisting of Sidewinder air-to-air, Harpoon air-to-sea and Stinger ground-to-air missiles -- contains no weapons that the Saudis do not have.

The sources noted the administration has promised not to attempt other arms sales -- containing such items as F15 jet fighters, M1 tanks and helicopter gunships -- to Saudi Arabia for at least a year. These arms are seen as a potentially greater threat by Israel, and sources said AIPAC decided to conserve political capital for a possible fight over a more comprehensive Saudi arms package.

In addition, the sources said, AIPAC wants to avoid a battle over the missiles while it remains undecided about whether to join an anticipated move later this year by Israeli supporters in Congress to reverse the 1981 sale of still undelivered Airborne Warning and Control System radar surveillance planes (AWACS) to Saudi Arabia. Some members of Congress argue that the sale should be voided on the grounds that Saudi leaders never fulfilled Reagan's 1981 promise that Saudi Arabia would work for the Middle East peace process.

In a letter published Saturday by The Washington Post, two leading proponents of the disapproval legislation, Sen. Alan Cranston (D-Calif.) and Rep. Mel Levine (D-Calif.), said the issue is not "a debate" between Congress and AIPAC but a question of Saudi Arabia's failure to help U.S. security interests through its refusal to endorse Arab-Israeli peace efforts.

Congressional sources said yesterday that because of that reason, opponents could continue trying to block the sale. But, if the administration does not face pressure from AIPAC on wavering lawmakers, it stands a better chance of preventing opponents from mustering the two-thirds vote needed to pass a disapproval resolution and override a certain presidential veto.

Delivery of missiles included in the package before Congress would not begin until 1989 and would stretch to 1991. Nevertheless, the administration argues the sale is urgent because of the immediate threat possibility that the Iran-Iraq war might spill over to Saudi Arabia and other Persian Gulf states.