President Reagan said last night he agreed "in principle" that a summit meeting with Soviet leader Yuri V. Andropov was desirable if it became clear that anything could be accomplished by a face-to-face meeting.

In a nationally televised news conference from the White House the president said that once adequate planning for a meeting between the superpowers had taken place, "I would welcome a summit just as I welcomed his [Andropov's] suggestion about continuing the talks on the reduction of arms."

Despite the conciliatory tone of the president's remarks, White House officials emphasized after the news conference that Reagan's basic suspicion of Soviet intentions remains unchanged and that he will still require "tangible evidence" of Soviet sincerity before he participates in a summit.

These officials confirmed that Reagan responded, "So what?" when he was first told of Andropov's suggestion for a summit meeting. They said that the president viewed the Soviet leader's vaguely worded offer as a public relations gesture and that Reagan was responding in kind last night.

Last week, White House spokesman Larry Speakes said that the administration saw "nothing new" in Andropov's proposal, which was contained in a written response to the editors of Hearst newspapers.

Other officials said that before Reagan would agree to participate in a summit meeting he would expect improvement in international behavior, particularly in Afghanistan, by the Soviets, better treatment of Russian dissidents and progress in the nuclear arms control talks at Geneva.

These officials stressed last night that the president's view was unchanged and that he had talked with advisers yesterday about spelling out his specific objections to Soviet international conduct at the news conference.

But the view that prevailed, one official said, was that the Soviets had seized the propaganda advantage with the widely reported summit plan. "The president didn't want to be throwing cold water on the idea of a summit," one official said.

Reagan responded with a similar conciliatory tone but no promises about an offer yesterday from the Warsaw Pact nations for a non-aggression pact. He said that such a pact was "something to be considered" but that he would want to consult with U.S. allies before making a formal reply.

As he was leaving the East Room after the news conference Reagan said in response to a question that Edward Rowny, the chief U.S. arms control negotiator at Geneva, had said that he thought a nuclear arms control agreement with the Soviets was possible within a year.

Disputing a Soviet contention that the United States is stalling the negotiations at Geneva, Reagan said they "know better. As a matter of fact, Gen. Rowny believes that within a year we've got a possibility of having an agreement on the Strategic Arms Reduction Talks ".

At the news conference the president responded for the first time to a question about whether the Soviet secret police and the Communist regime in Bulgaria were behind the attempt to assassinate Pope John Paul II.

"I know that the Italians are investigating, and in view of their procedures and their handling of the Gen. [James L.] Dozier case, I have great confidence in their abilities," Reagan said. "But as long as they are investigating, I don't think it would be proper for me to make a comment on this because I would have no information except the same things that all of us know about this."

When Reagan was asked what impact it would have on Soviet-American relations if the reports of Soviet and Bulgarian involvement proved to be correct, he replied:

"I think that it certainly would have an effect. I think it would have an effect worldwide, and I'd meet that problem when we got to it."

Former national security affairs adviser Zbigniew Brzezinski said Monday that he believes the Soviets were behind the plot to kill the pope.

The president fended off a question about the slow progress of Middle East peace talks by saying that the administration had not expected rapid progress.

"We would have liked to have this whole thing move faster, but in view of the situation, not only in Lebanon but the whole Middle East, we never had any illusions that this could be done overnight, and the negotiations are under way now that will lead to the removal of the foreign forces," Reagan said. Reagan also was asked about worry on the part of the financial community over the huge debts of Latin American situations and acknowledged his concern.

"Of course, there's a risk," he said. "I think it's a touchy financial situation worldwide just as this recession is worldwide.

"We have taken a number of steps with regard to the international monetary funds that are available for bailouts . . . . We have taken unilateral action with some of our neighbors, as you know, to tide them over and help."

Reagan was referring to efforts to help Mexico with advance oil purchases and to aid Brazil with a short-term loan.

While acknowledging that there would be "some very severe financial problems" if there were widespread default, the president gave a more optimistic assessment of the future situation in Latin America.

"I'm inclined to believe we're going to come through this all right," he said.