The Reagan administration said yesterday that Libyan leader Muammar Qaddafi's declaration that he will train and equip Arab guerrillas for "suicide missions" is proof of U.S. charges that "he has, in fact, been training terrorists for years."

"Qaddafi is his own smoking gun," Secretary of State George P. Shultz was quoted as saying in reaction to Qaddafi's threats against Israel and the United States during a long, rambling speech in Tripoli Wednesday night. Qaddafi dropped the conciliatory tone he had taken toward the United States in recent days and proclaimed Libya "a base for the liberation of Palestine."

His public vow to train and arm terrorists came as Deputy Secretary of State John C. Whitehead was beginning a trip to Canada and Europe aimed at persuading U.S. allies that Libya was involved in the terrorist attacks at the Rome and Vienna airports last month.

However, while U.S. officials cited Qaddafi's remarks as an admission of support for terrorism, their reaction was essentially disdainful, apparently taking their cue from President Reagan's characterization of Qaddafi as "flaky."

Some officials said the administration wants to avoid a heavy-handed propaganda exchange and believes the U.S. case can be made better by the evidence being carried by Whitehead and by Qaddafi's actions and statements.

State Department spokesman Bernard Kalb said Shultz had called Qaddafi "his own smoking gun," and added: "Qaddafi's statements should have been put in the past tense . . . . He has, in fact, been training terrorists for years. A new element in his speech is that he publicly admitted support for terrorism."

Shultz, interviewed on CBS' "Morning News," said, "What Qaddafi should have said is that he will continue to train. Qaddafi's involvement in terrorism is nothing new. It isn't some new thing he's going to start. He's been doing this."

Defense Secretary Caspar W. Weinberger said Qaddafi had "confirmed" what "we've been saying all along," that his country "is a base for terrorism. I don't think it escalates the situation."

At his first general news conference in four months, Weinberger declared that the two aircraft carriers and escorting warships deployed by the United States in the Mediterranean are an "appropriate" force and need not be expanded.

Pentagon officials added that the carrier USS Saratoga and its escorts were cruising off Lebanon, while the carrier USS Coral Sea is conducting North Atlantic Treaty Organization maneuvers with Marines on the western coast of Italy. Both carriers have A6E bombers which, with midair refueling, could reach targets in Libya.

Weinberger said the United States has "a good idea" about the location of some terrorist bases in Libya. But, in response to repeated questions about why the United States does not retaliate militarily against Libya, he opposed the idea of "an indiscriminate response."

State Department officials, reacting to reports that Soviet warships have arrived in Tripoli harbor and that the Soviet Union may be accelerating weapons shipments including antiaircraft missiles to Libya, said the Soviet actions did not appear to exceed normal patterns of Soviet-Libyan cooperation.