Representatives of the House and the Senate cut 23 percent from the superconducting supercollider's 1991 budget Friday as part of Congress' deficit-reduction effort.

The size of the cut stunned the atom smasher's supporters and threatened its long-term survival.Members of the House and Senate appropriations committees cut the collider's budget by $75 million to $243 million. The committee freed $25 million that had been set aside for later use on the collider, an action that reduced the effect of the cut to $50 million.

The cut will delay the collider's completion, now scheduled for 1998, and raise its cost, proponents said. And both those factors will harm its support in Congress.

The collider, housed in a 54-mile underground ring to be built south of Dallas, would be used by scientists to study subatomic matter.

Both the House and the Senate earlier approved spending $318 million on it in 1991. But that was done without an overall budget outline.

Congress on Monday approved an outline telling committees to develop spending cuts and tax hikes to meet a deficit-reduction target of $45 billion in 1991.

The appropriations conferees had been asked to cut $750 million from the 1991 appropriations bill for energy and water projects. The atom smasher, still in the beginning stages of construction, is 10 percent of that savings.

Randy Erben, director of the Texas Office of Federal-State Relations, said state officials may consider making up the $50 million. But, he added, "without the reimbursement guarantee, we'd be essentially buying a pig in a poke."