President Reagan reached a compromise yesterday with key Senate opponents of a proposed arms sale to Saudi Arabia, apparently assuring congressional support for a $1 billion package that will exclude the most controversial item -- 1,600 Maverick antitank missiles -- but include 12 additional F15 jet fighters.

At the same time, the White House agreed to drop plans to provide sophisticated Stinger surface-to-air missiles to the Persian Gulf sheikdom of Bahrain.

Four key senators who had opposed the administration's initial $1.4 billion proposal announced the compromise agreement, indicating they would support it. One, Sen. Howard M. Metzenbaum (D-Ohio), predicted the accord would avoid another confrontation between Congress and the White House over U.S. arms sales to the Saudis.

The agreement came after two weeks of negotiations between Senate opponents and Reagan's national security adviser, Frank C. Carlucci. Secretary of State George P. Shultz attended a final White house meeting on the agreement yesterday with congressional leaders.

It comes as the administration seeks added Saudi support for U.S. military forces operating in the Persian Gulf to protect Kuwaiti oil tankers and facing a threat from Iran.

"This may not satisfy everyone, but I think it will be sufficient to head off a fight in the Senate," said Senate Minority Leader Robert J. Dole (R-Kan.). "I think it's probably going to be approved."

Sen. Bob Packwood (R-Ore.), cosponsor of a Sept. 25 letter to Reagan opposing the sale signed by 64 senators, said the compromise was "as satisfactory a result as we are going to get under the circumstances . . . . We have decided not to contest the sale."

The other key senator in yesterday's final talks was Rudy Boschwitz (R-Minn.).

Senate Majority Leader Robert C. Byrd (D-W.Va.), who had written a separate letter of opposition, said he was "pleased" by the agreement.

The compromise came after 68 senators -- enough to override a presidential veto -- had expressed opposition to the administration's original $1.4 billion Saudi arms sale proposal and appealed to Reagan to avoid another bruising confrontation with Congress over a sale. Israel and the American Israel Public Affairs Committee, a pro-Israel lobbying group, had strongly opposed the sale.

Within hours of reaching the agreement and after a separate meeting with the Saudi ambassador, Prince Bandar bin Sultan, the president sent an informal notification to Congress of his intent to sell Riyadh 12 F15C/Ds; 93 artillery ammunition carriers, and enhancement equipment to modernize Saudi F15s and M60 tanks to a level "compatible with U.S. equipment of the same model."

The value of the package is expected to be about $1 billion.

The Arms Export Control Act requires the White House to provide Congress a 20-day informal notification, followed by a 30-day formal notification. During the latter period, Congress can pass a resolution of disapproval killing the sale, although the legality of this procedure is in dispute.

A White House statement termed the sale an "essential part" of U.S. strategy to protect the Saudis' "legitimate defense needs" amid heightened threats by Iran to both countries' military and economic interests in the gulf.

Reagan will keep the issue of Saudi Arabia's need for Maverick missiles "under very close review in light of threats to Saudi security," the statement said.

"The president has personally assured the Saudi government that in the event of an emergency, the United States would provide Mavericks from American stocks with appropriate notifications to Congress," it said.

A source close to the Saudi government said the Saudis "went along with it {the compromise} across the board."

The White House tried in June for congressional approval to sell 1,600 Maverick missiles, worth $360 million, but withdrew the proposal in face of overwhelming Senate opposition. Saudi Arabia has about 2,500 older-model Mavericks but the administration sought to sell the latest version.

Carlucci, in his negotiations, failed to gain support for the sale of 800 Mavericks, leaving the White House with little choice but to drop them from the package.

Under yesterday's compromise, the 12 additional F15s will be kept in the United States and sent to Saudi Arabia only to replace any Saudi losses from its existing force of 60 F15s. In effect, Senate opponents and the White House have agreed to a ceiling of 60 F15s deployed in the kingdom at any given time.

Saudi Arabia presently is three planes under the limit.

Senate opponents had also sought a Reagan commitment that in turn for their support for the sale of the 15 additional F15C/Ds, none of the latest model F15Es will be made available to the Saudis. It was not immediately clear whether the White House had agreed to this as part of the compromise. Staff writer Tom Kenworthy contributed to this report.