President Reagan said last night he would not give up testing or development for the Strategic Defense Initiative (SDI), his missile defense program, in exchange for deep reductions in Soviet offensive nuclear missiles.

In a nationally televised news conference, Reagan said he intends to urge Soviet leader Mikhail Gorbachev at the Geneva summit in November to join the United States in a shift toward defensive weapons. Reagan said his program could "rid the world of the nuclear threat" and thus is "too important to the world" to trade for reductions in Soviet missiles.

Reagan appeared to be rejecting publicly for the first time such a trade-off, which has been suggested by some in the administration, as well as many outside experts, as a way to break the long stalemate in superpower arms negotiations.

The president, appearing relaxed in his first formal news conference since cancer surgery in July, also declared that he would strongly resist protectionist trade legislation pending on Capitol Hill, calling it a "mindless stampede" and a "one-way trip to economic disaster."

Reagan's warning on protectionism came as the Senate Finance Committee approved legislation to make Japan and other countries open their telecommunications markets to U.S. suppliers or face stiff retaliation.

The president also defended as adequate his budget for research on acquired immune deficiency syndrome (AIDS) and expressed sympathy for children with the disease as well as for parents who are demanding that such children be kept out of the classroom.

Reagan said that rifts in the Republican Party have been healed and pointed to lawmakers who endorsed his last-minute compromise on economic sanctions against South Africa. Reagan also brushed aside criticism of the sanctions he did impose, saying that "when you're standing up against a cellophane wall and you're getting shot at from both sides, you must be doing something right."

The news conference, Reagan's 32nd formal session since taking office, was dominated by questions about the Nov. 19-20 summit with Gorbachev and what approach Reagan would take to nuclear weapons issues in his first meeting with a Soviet leader.

Reagan's space-based missile defense program, which he first proposed in March 1983, has been the subject of increasing speculation about a possible arms trade-off at the Geneva summit, fueled in part by hints from Gorbachev to a group of U.S. senators that Moscow would be interested in such a deal. Former president Richard M. Nixon said in a recent essay on the summit in the journal Foreign Affairs that under certain circumstances Reagan's missile defense system would be the "ultimate bargaining chip."

But Reagan appeared last night to repeatedly throw cold water on such a trade-off. He reiterated that he does not see the missile defense program, now in the research phase, as a "bargaining chip" in talks with the Soviets. Reagan added, however, that he would offer the Soviets "a great deal of room for negotiation" once the system is ready for deployment, but that flexibility would be to share the system, not curb it.

Reagan was asked whether he was ruling out any deal with the Soviets on testing, deployment, research and development of the missile defense program. He replied that research would continue and noted that it "is not in violation of any treaty." In the past the administration has said the program does not violate the restrictions imposed by the 1972 Antiballistic Missile (ABM) Treaty, which limits development, testing and deployment of defensive systems.

Earlier this year, the Defense Department, in a report to Congress, sought to define a legal "gray area" in the ABM treaty that would allow some testing of the Reagan program.

Reagan said last night that he views the testing and development of components of the missile defense system as "as legitimate part of research." Reagan said he would consider stopping short only of deployment, the final phase and then for the purpose of discussions on how the system could be shared with U.S. allies and the Soviets.

The president said, "This is too important to the world to have us be willing to trade that off for a different number of nuclear missiles when there are already more than enough to blow both countries out of the world."

Reagan said "the United States is still well behind the Soviet Union in literally every kind of offensive weapon," although officials of his own administration have said that U.S. cruise missiles, submarine-based missiles and bombers are all superior to Soviet models.

Discussing the summit, Reagan chided the Soviets for not responding to what he described as a series of at least six different U.S. proposals for reducing the number of nuclear warheads.

"As a matter of fact, the side that has not been negotiating -- with all our months and months of meetings in Geneva and the arms talks -- is the Soviet Union," he said, adding that the Soviets have "come back with nothing."

Responding to questions about expecations for the Gorbachev meeting, Reagan said he was "worried" about anticipation in this country that the summit could produce a "near miracle." Reagan said he takes the meeting "very seriously" and wants it to go beyond just a "get-acquainted" session.

Commenting on the intensified Soviet courting of public opinion in the West, Reagan asserted that he had not participated in "a propaganda game" and said the Soviet effort "is a continuation of a long-time campaign aimed mainly at our allies in Europe and in an effort to build an impression that we may be the villans in the piece and that they're the good guys."

"I don't think it has registered with our allies and I'm not going to take it seriously at all," he added.

The president also insisted that the recent test of the U.S. antisatellite weapon against a target in space was not designed as a show of strength in advance of the summit.

Reagan opened the news conference, held in the White House East Room, with a statement warning of the dangers of legislation to limit imports, recalling the Smoot-Hawley tariffs that contributed to the Depression during his youth. "I've seen and felt the agony this nation endured because of that dreadful legislation," Reagan said. "If we repeat the same mistake, we'll pay a price again."

Congress is expected to act soon on legislation designed to protect the U.S. textile industry, and Reagan was uncompromising in his opposition last night to such bills, despite recent conciliatory signals sent to Capitol Hill on the subject of trade.

"Protectionist tariffs would invite retaliation that could . . . . deliver an economic death blow to literally tens of thousands of American family farms," Reagan warned. He cautioned against risking what he described as economic progress of the last 4 1/2 years by "starting down on a slippery slope of impulsive acts and imprudent judgment."

Government statistics published this week showed that the United States had become a net debtor nation for the first time in 71 years. But Reagan said he was skeptical of the numbers, claiming they gave a "false impression" and that there are "weak spots" in the statistics he did not identify.

Reagan looked to history to suggest the current trade deficit, expected to hit a record $150 billion this year, is not an impediment to the economy.

He said the United States ran a trade "imbalance" in the period from 1790 to 1875 when it was becoming a "great economic power," and he went on to argue that despite today's large trade deficit, the U.S. economy is creating jobs. "This recovery, the greatest one we've known in decades, has been done with this same trade imbalance," he said.

Furthermore, he said, during the Depression the United States had a trade surplus. "So I think this has been exaggerated," he said. "And it isn't a case of us being a debtor nation."

Questioned whether the administration was devoting enough money to research on AIDS and whether he would support a massive research effort, Reagan said, "I have been supporting it for more than four years now."

He said the $100 million budgeted for this year and $126 million next year shows "this is a top priority with us." Reagan, who is briefed by aides before every news conference, appeared to be prepared last night for questions on the disease, which has generated intensifying attention in the news recently.

"I think with our budgetary constraints and all, it seems to me that $126 million in a single year for reseach has got to be something of a vital contribution," he said.

Commenting on the recent controversy over whether children with AIDS should attend school, Reagan said, "I can understand both sides of it."