WASHINGTON — WASHINGTON -- President Clinton signed a $265 billion defense authorization bill yesterday, while promising he would not enforce a "blatantly discriminatory" provision of the bill requiring the Pentagon to discharge troops who have the virus that causes AIDS. White House officials said the president felt that he had no choice but to sign the authorization bill because it contained a variety of other provisions that he considered vital to national defense and troop morale, including a 2.4 percent military pay raise. Under the bill, the Defense Department is compelled to begin ousting infected service members within six months regardless of their ability to perform their jobs. The Pentagon has estimated that slightly more than 1,000 service members are infected with HIV, the AIDS virus. Mr. Clinton vowed yesterday to work with Congress "to repeal this provision before a single service member is discharged from the service." White House lawyers said the discharge provision was unconstitutional and would almost immediately draw a court challenge from advocacy groups. They said they were hopeful that federal courts would block the provision from taking effect. The president has ordered the Justice Department not to defend the provision in court. If the courts do not act, however, the military careers of HIV-infected service members would come to an end later this year -- soldiers and other military employees receive regular blood tests, making it impossible to hide the condition -- even though the Pentagon holds that virtually all are fit for duty. The provision requiring their ouster was placed in the bill by Rep. Bob Dornan, a California Republican who is seeking his party's presidential nomination. Mr. Dornan argued that the combat readiness of the military is harmed by the presence of troops with HIV, and he said Friday that President Clinton was "deferring to the wishes of a vocal minority who donate heavily to his presidential campaign" by seeking to overturn the provision. Mr. Clinton vetoed an earlier version of the appropriations bill largely because it required the deployment of a multibillion-dollar missile defense system by 2003. The White House believes the provision was a violation of the 1972 anti-ballistic missile treaty, and it was deleted in its entirety from the bill signed yesterday. The new bill contained several other appropriations not requested by the White House, including $493 million originally earmarked by lawmakers to build new B-2 stealth bombers beyond the fleet of 20 requested by the Air Force. The White House has said that it would use the money not to build new bombers, but to upgrade the existing fleet of B-2s. Over the president's objections, the bill also placed a ban on abortions at American military hospitals abroad. Abortions have long been banned at military hospitals in the United States, but they were permitted at military installations abroad out of concern that safe, private abortion services were not always available overseas.