The Senate Foreign Relations Committee, after three hours of emotional debate, yesterday approved controversial revisions to the 1972 extradition treaty between Great Britain and the United States that would make it harder for Irish terrorists to win U.S. sanctuary.

The senators voted 15 to 2 after agreeing on amendments that sought to distinguish between political rebels -- to whom the United States has traditionally offered safe haven -- and terrorists, for whom the senators said extradition should be speedy.

The compromise, which still needs approval from the full Senate, pleased the Reagan administration and delighted the British Embassy, where an official said Prime Minister Margaret Thatcher "will be very pleased." She and President Reagan had lobbied for the treaty in recent weeks, asking senators to pass it in "appreciation" of Britain's help in the U.S. bombing raid against Libya last April.

The compromise also received qualified support from Sean McManus of the Irish National Caucus, which stridently opposed the Reagan administration's original treaty proposal. McManus called yesterday's vote "a serious diplomatic setback" for Great Britain.

The American Civil Liberties Union denounced the compromise as "cutting the heart out" of a 1972 treaty that bars extradition of people charged with politically motivated crimes of violence that often accompany domestic rebellions, such as murder and hijackings.

"Countries will now line up and ask for similar protection from their revolutions, one by one," said ACLU spokeswoman Susan Benda.

Irish Republican Army fugitives in the United States have cited existing political exemptions in fighting extradition to Great Britain. The Reagan administration had proposed removing all exemptions and giving the executive branch full authority to approve extradition requests.

The pact had been stalled since last June because of resistance from Democrats and Sen. Jesse Helms (R-N.C.), who feared it would set a precedent for allowing leftist governments in Afghanistan and Nicaragua to extradite their opponents.

The key compromise, constructed by Chairman Richard G. Lugar (R-Ind.), and Sen. Thomas F. Eagleton (D-Mo.), narrowed the exemption list but added a provision guaranteeing U.S. courts jurisdiction over extradition. Three liberal Democrats were brought on board with the inclusion of language in the committee report giving U.S. courts the right to consider motives for the extradition request and the quality of courts in the country making the request.

The pact now spells out offenses that cannot be called politically motivated: murder, voluntary manslaughter, injurious assault, kidnaping, hostage-taking, or the use of bombs, grenades, rockets, firearms, letter-bombs or incendiary devices.

The committee voted, 15-2, to defeat a Helms amendment that would have included only crimes against civilians. "Rebellion almost always involves attacks against military installations," he said, asserting that "the American Revolution would have been outlawed" under the proposed pact.

Eagleton countered in an emotional speech that it was "a disgrace" to "compare parcel bombers to George Washington." He said "some terrorists wear hoods like an Arab. Some terrorists have rosy cheeks and speak with a brogue."

Mark E. Pellew, counselor for congressional affairs at the British Embassy, said the treaty revisions "could make a difference" in two pending extradition cases.