The Republican-controlled Senate Armed Services Committee faces the prospect today of handing President Reagan his first major setback on the B1 bomber by slowing its production and refusing to authorize multiyear procurement in the fiscal 1984 defense authorization bill.

A bipartisan combination on the committee has contended in closed markup sessions that cutting $888.7 million from the B1 account is crucial to holding the defense budget to after-inflation growth of 5 percent between fiscal 1983 and fiscal 1984. Reagan seeks 10 percent growth.

Last week, sources said, Chairman John G. Tower (R-Tex.) postponed a vote on B1 funding in hopes that the Defense Department would suggest offsetting cuts for the $888.7 million. Defense Secretary Caspar W. Weinberger has steadfastly refused to offer further reductions and is expected to stick to that course in regard to the B1.

In anticipation that Weinberger would not offer a "hit list" of projects, several senators have drawn up their own lists to make up for the $888.7 million that would be saved by authorizing B1 money only for fiscal 1984 and holding the future production rate to 36 bombers a year.

Reagan's plan calls for accelerating production from 10 in fiscal 1984 to 34 in fiscal 1985 and 48 in fiscal 1986. The other eight that comprise the full order of 100 B1s result from congressional authorization of one B1 in fiscal 1982 and seven in 1983.

B1 opponents assert that production will not stop at 100 as planned, partly because so many jobs are tied to the program.

The administration is seeking permission in this year's defense bill to negotiate three years of production estimates to save about $600 million. Congressional opponents contend that the multiyear approach would commit the government to volume production at too early a stage.

Congress authorizes procurement one year at a time for most weapons, although it has made exceptions. Two weeks ago, the Democratic-controlled House voted, 252 to 171, against an amendment to forbid multiyear B1 production.

Of the $888.7 million that the Armed Services subcommittee on strategic and theater nuclear forces recommended be cut from the administration's B1 request, about half would result from forgoing multiyear procurement and the rest from stretching the production run.

That amount is the biggest item on Republican and Democratic hit lists before the committee, excluding the $1.7 billion the administration saved by changing its deployment scheme for the MX missile.

Other cuts on both hit lists include deletion of money projected by the Navy in cost increases on its submarine missile program, $375.8 million from the Air Force KC135 tanker program and $147.1 million from the Army's missile-defense research because Reagan has called publicly for more advanced technology.