The Senate voted overwhelmingly yesterday to allow women to fly combat missions and also authorized suspension of sex-based restrictions for land and sea combat roles while a presidential commission studies the issue of women's assignments in the military.

The provisions were approved as the Senate began consideration of a $291 billion defense authorization bill for next year and, as it worked late into the night, defeated the first two of several amendments aimed a scuttling or modifying a major new plan for deployment of an antimissile defense system.

The surprise vote on women in combat was the most far-reaching congressional action thus far to end curbs on women in combat in light of their high-profile roles in the Panama and Persian Gulf conflicts.

While the House voted in May to drop statutory restrictions that prohibit women from flying combat missions, the Senate Armed Services Committee had rejected any permanent change in law in favor of a study by a 15-member, White House-appointed commission that would report to Congress by Dec. 15, 1992.

The commission proposal drew fire as a delaying tactic, prompting Sens. William V. Roth Jr. (R-Del.) and Edward M. Kennedy (D-Mass.) to counter with the House plan, which would give the Air Force, Navy and Marines the authority the Army now has to determine their own rules on assignment to combat missions.

The Senate's action appeared to assure that the compromise defense bill eventually approved by Congress will permit women to fly combat aircraft, and Senate sponsors of the study commission proposal are expected to push hard for its acceptance by the House. While senators did not anticipate Pentagon objections to the women-in-combat provisions, various other provisions of the Senate and House defense bills have prompted Bush administration objections.

"Forty years ago Congress imposed a rule which now prevents women from serving as combat pilots," said Roth. "This congressional restriction is as old and outdated in today's military as a World War II propeller plane."

As an alternative to the Roth-Kennedy proposal, Sen. John Glenn (D-Ohio), who pushed for the commission study in committee, proposed the temporary waiver of all restrictions to allow test assignments of women to combat positions while the commission was conducting its study.

This would enable the commission to evaluate the assignment of women at all levels of land, sea or air service, based on actual tests, and to resolve such questions as whether women should be subjected to mandatory as well as voluntary combat service, Glenn argued.

Even though they were debated as though they were rival approaches, the Senate approved both proposals by huge margins in what appeared to be a clear indication of Senate support for major liberalization of military policy toward assignment of women.

"This is about as clear a statement of what the Senate wants as you can get around here," said Kennedy after the two votes.

After a sometimes emotional, testy debate on the issue, the Senate voted 96 to 3 to approve Glenn's proposal for a temporary waiver of rules against women in combat, with the dissenting votes coming from Democrats Robert C. Byrd (W.Va.), Howell Heflin (Ala.) and Lloyd Bentsen (Tex.).

Then it approved the Roth-Kennedy proposal to allow women in combat aircraft by voice vote after a 69 to 30 test vote against scuttling the plan. Most of the opposition to the proposal came from older and more conservative members. Bentsen supported this plan, while Heflin and Byrd did not. The only Washington-area senator voting against the Roth-Kennedy proposal was Sen. John W. Warner (Va.), ranking Republican on the Armed Services panel.

The nation's 2 million-member military forces include nearly 223,000 women, including 35,000 who served in the Persian Gulf War. Eleven women died in the war, including five in combat. While women are not allowed to serve in combat aircraft, combat ships or in ground units likely to encounter close-quarter combat, they serve now in potentially dangerous support roles such as flying transports or sailing on support ships.

Until now, women have made up a very small fraction of military aviators, but they have gradually broken into elite assignments in one of the military's most rigid bastions of male supremacy.

There are 248 women pilots in the Navy, compared to 12,040 men, and 106 women who serve as "back-seaters," or weapons and navigation officers, compared to 6,727 men. There are 325 women qualified as pilots and 122 as back-seaters in the Air Force, compared to 20,130 and 9,370 men. In the Army, 362 women fly helicopters, representing about 3 percent of all Army aviators. No women have been permitted to fly jets or helicopters in the Marine Corps.

A series of proposals to scrap or modify the proposed revisions in the Strategic Defense Initiative (SDI) were pending last night, including ones aimed at blocking deployment of missile interceptors, at preventing any breaches of the 1972 Anti-Ballistic Missile (ABM) Treaty and at cutting proposed increases in SDI funding.

At issue in the debate over antimissile defenses was a plan to deploy 100 antimissile interceptors at a base in Grand Forks, N.D., by 1996 as the first phase of a broader, multiple-site deployment that would require renegotiating or breaching the ABM Treaty.

The plan, which would also increase spending for SDI while restructuring it to emphasize ground defenses instead of "Star Wars," or space-based, defenses, was proposed by Armed Services Committee Chairman Sam Nunn (D-Ga.) and Warner.

Describing the plan as a threat to "perhaps the most important agreement we've ever signed" with the Soviet Union, Sen. Albert Gore Jr. (D-Tenn.) proposed to jettison the deployment plan in favor of more limited antimissile defenses that would not breach the ABM Treaty. To threaten the ABM pact on the same day that the United States and Soviets were signing the new Strategic Arms Reduction Treaty (START) to reduce offensive weapons could lead to "one of the most serious mistakes that this country has ever made," said Gore.

Gore's proposal was rejected, 60 to 39. The Senate then rejected, 56 to 43, a proposal from Sen. Jeff Bingaman (D-N.M.) to sanction only the installation at Grand Forks and rule out all others unless the ABM Treaty is renegotiated to accommodate them. Several more proposals remained to be voted on later.