House-Senate negotiators announced agreement yesterday on a long-delayed defense authorization bill for this year that sharply cuts President Reagan's spending requests and anticipates an arms-control compromise that would require status-quo observance of key treaties.

The agreement allows spending of as much as $296 billion for military operations and weaponry for the fiscal year that started Oct. 1, depending on the outcome of current budget negotiations.

Even that maximum figure represents a cutback of $16 billion from Reagan's request and a reduction in Defense Department spending authority, after accounting for inflation, for the third consecutive year.

If budget talks being held separately by administration and congressional negotiators result in requiring heavier-than-anticipated savings from defense, losses to the Pentagon would be even more severe. They include cancellation of at least two major weapons programs, the Navy's A6 bomber and the Marines' Harrier vertical-takeoff aircraft.

Collapse of the budget effort would result in even broader and deeper cuts under across-the-board reductions mandated by the Gramm-Rudman-Hollings budget law and could lead to widespread program terminations. Under one scenario, weapons-procurement accounts could by cut by nearly 20 percent.

The fiscal 1988 defense agreement authorizes $3.9 billion for the Strategic Defense Initiative (SDI), $1.8 billion less than Reagan's request. But it would fully fund two new aircraft carriers and pave the way for a 3 percent military pay raise. The administration had sought a 4 percent increase.

It emphasizes military readiness, conventional weaponry advances and high-technology research over development and procurement of strategic weapons systems, according to negotiators. It also attempts to exert tighter congressional control over weapons that have encountered major problems. These range from the B1 bomber to the Bradley Fighting Vehicle.

The agreement was worked out after months of intense dispute between Congress and the White House over arms-control provisions, with Reagan threatening to veto the bill if they were included.

A tentative arms-control compromise was worked out in consultation with national security adviser Frank C. Carlucci, who has been nominated to be defense secretary. It remains unclear whether Reagan will accept the final terms of the compromise.

"It is my hope and expectation that he will sign it . . . but there are no guarantees," Senate Armed Services Committee Chairman Sam Nunn (D-Ga.) said.

House Armed Services Committee Chairman Les Aspin (D-Wis.) said, "The administration position is not that they like this deal . . . . It's a question of how badly do they dislike it."

Sen. John W. Warner (R-Va.) said he thinks that "the veto strategy will be shelved" if House negotiators give final approval next week to details of the arms-control provisions.

Under tentatively approved terms, Congress would drop insistence that Reagan observe strategic-weapons limits in the unratified 1979 SALT II treaty and restrict SDI testing to a "narrow" interpretation of the 1972 Antiballistic Missile (ABM) Treaty.

In return, the administration would be required to dismantle a The agreement was worked out after months of intense dispute over arms-control provisions.

Poseidon nuclear missile submarine to assure that the United States does nothing more to fall out of compliance with SALT II.

The United States breached the treaty last year when it deployed additional B52 bombers carrying nuclear cruise missiles, and the administration plans deployments that would further exceed the limits.

Also, the administration would have to limit SDI tests to those that it previously outlined to Congress, all of which would fall within the traditional interpretation of the ABM agreement.

The administration has been pushing for a broader interpretation that would allow expanded tests, but none were planned for this year.

House-Senate negotiators agreed to these provisions with the knowledge, though not acquiescence, of the White House in the case of SALT II limits, sources said. Final agreement on all arms-control provisions was held up in a related dispute over House-proposed bans on nuclear tests and testing of antisatellite (ASAT) weapons in space.

Conferees reportedly agreed to continue the current ban on ASAT tests but drop the demand for a nuclear test ban.

However, the administration and House Democrats remain at odds over related issues, including Democratic demands for progress on developing verification techniques that could pave the way for a ban on nearly all nuclear tests, an issue before U.S.-Soviet negotiators.

A meeting to resolve these issues is expected Tuesday.

The authorization bill sets out framework and limits for military programs; actual funding, which may be lower, will be worked out in an omnibus government spending bill that Congress is scheduled to pass next month.

In a step toward military-funding reform, the authorization bill covers two years for the first time, including two-thirds of what will be required for fiscal 1989.Staff writer Molly Moore contributed to this report.