Members of the Senate Armed Services Committee, while treating the administration's defense budget request with more respect than it has met elsewhere in Congress, told Defense Secretary Caspar W. Weinberger yesterday that his spending proposal will be cut.

Senators from both parties, including John W. Warner (R-Va.) and J. James Exon (D-Neb.), indicated that they believe that an after-inflation increase of 3 percent in the defense budget may be the best compromise between a spending freeze and Weinberger's request for about 9 percent real growth.

Sen. Sam Nunn (D-Ga.) said, "The resources simply aren't going to be there over the next four or five years to carry out the program Secretary Weinberger is laying out here."

The administration's plan seeks $2 trillion in budget authority for the Pentagon during the next five years, beginning with $313.7 billion in fiscal 1986.

Even conservative committee chairman Barry Goldwater (R-Ariz.) told Weinberger that the defense budget request "can and will be reduced."

But Goldwater, who only two months ago said that the military could accept a spending freeze and that President Reagan should give up on production of the MX missile, set the tone for committee Republicans when he argued against major reductions.

"Our commitment to defense has convinced the Soviets that it is in their interest to negotiate," Goldwater said, echoing a key administration argument. "Therefore, now is not the time to be talking about major defense reductions or the unilateral cancellation of strategic programs."

Weinberger defended his budget request with his usual mixture of humor, testiness and lengthy answers referring to the Soviet threat and the dangers of cutting the defense budget. As in the past, he brought charts depicting tall red columns representing Soviet force strength towering over small blue columns representing U.S. forces.

"It would have been easy for the president to have sought immediate deficit savings through reductions to defense programs," Weinberger said in his prepared statement, "but the result would be an unavoidable weakening of our defense posture now and into the future." Sen. Carl Levin (D-Mich.) noted that Weinberger has issued similar warnings every year, that Congress has cut the budget every year anyway and that Reagan claimed during his election campaign that, despite the cuts, "our defenses are repaired."

Levin also disputed Weinberger's contention that increases in defense spending are an unavoidable response to Soviet military spending.

"As a matter of fact, we had bigger real increases in our defense expenditure than the Soviets did in the last third of the '70s," Levin said. "In fact, for the years 1977 to 1984, our growth was almost twice that of the Soviet Union."

Weinberger responded that Soviet expenditures are difficult to measure and that what matters is output of tanks, planes and other weapons, in many of which the Soviet Union continues to lead.

Nunn questioned why the Soviet Union leads in production if it is spending less, to which Weinberger responded that "four or five or six men in the Kremlin" can more efficiently direct resources toward their goal of "the establishment of communism throughout the world."

"You're saying that a centralized system in a dictatorship is more efficient than free enterprise?" Nunn asked.

"No, sir, I'm not," Weinberger said. Later, he added that the Soviets can spend less in part because they depend on "slave labor" and cheap conscripts.