WASHINGTON — House Republican leaders suffered a surprise defeat Friday as an unlikely coalition of liberals and abortion foes defeated a $243 billion defense spending bill.

Breaking from the GOP leadership, the abortion foes, many of them freshmen Republicans, opposed the lengthy spending bill because of a single clause weakening an anti-abortion provision in the legislation.

“Saint Peter, on my judgment day, will not ask me about the B-2 bomber or my defense votes,” said Rep. Robert Dornan, R-Calif., author of the original provision. “He will ask me about my votes on human life.”

The final version of the bill — worked out in conference with Senate negotiators — retained Dornan’s provision prohibiting abortions in overseas military hospitals. However, it also contained a caveat that it would become law only if an identical provision were passed in a companion defense authorization bill. That legislation is bogged down in House-Senate negotiations and its final passage is in doubt.

Liberal Democrats, meanwhile, rallied around a veto threat from President Clinton. A letter from the Clinton’s budget director, Alice Rivlin, to House Speaker Newt Gingrich indicated the president would veto the bill because it called for spending $6.6 billion more on defense than he requested.

“We simply cannot allocate nearly $7 billion more than we need at this time for defense, and starve our needed investments in education and training and other priorities,” Rivlin wrote in the letter delivered Friday afternoon.

Defeat of the bill in a 267-151 vote means the measure must go back to House-Senate negotiations for possible revision. The Senate has not yet voted on it. A total of 130 Republicans joined 136 Democrats and one independent in rejecting the bill. Voting for it were 98 Republicans and 53 Democrats.

Rep. Jim B. Longley Jr. voted for the bill; Rep. John Baldacci voted against it.

On Sept. 7, when the House passed its own version of the bill, only 19 Republicans voted against it.

Friday’s lopsided vote came despite the exhortations of senior Republicans who have become accustomed to party discipline this year. Rep. Bill Young, R-Fla., chairman of the House Appropriations national security subcommittee, called the measure “one of the major cornerstones of our `Contract with America.”‘

It was to no avail. Republicans could not even muster a majority of their own members against a formidable lobbying campaign mounted by anti-abortion organizations such as the Christian Coalition and the National Right to Life Committee. The groups operated phone banks and organized letter-writing drives that swamped the offices of sympathetic lawmakers.

Other Republicans objected to a section of the bill that would weaken a provision urging Clinton to gain congressional approval before sending U.S. ground troops to Bosnia.

Still others voted against it because it would fund more B-2 bombers. Republicans Steve Largent of Oklahoma and Peter Hoekstra of Michigan circulated a “Dear Colleague” letter opposing the third Seawolf submarine.

“I think the B-2 is very vulnerable,” Young said. “In effect, the president won today.”