President Reagan, responding to Israel's claim yesterday that the United States is seeking to break the deadlock over Palestinian guerrillas in West Beirut by Friday, said last night, "There are no deadlines that have been set of any kind."

At a nationally televised news conference, the president appeared to be stepping away from Israeli Prime Minister Menachem Begin's statement that U.S. special envoy Philip C. Habib has promised to seek "an unequivocal commitment" from the Palestinians by Friday that they will leave West Beirut.

Reagan did not refer directly to Begin's assertion in Jerusalem. While discussing Habib's efforts, he said, "Contrary to some reports or rumors today, there are no deadlines that have been set of any kind."

"There's nothing we would like more than to see an end to the bloodshed and the shelling," Reagan said in reference to cease-fire violations that have caused death and destruction in recent days. "We still stay with our original purpose, that we want the exodus of the armed PLO out of Beirut and out of Lebanon."

Despite the fact that negotiations over the PLO's departure have dragged on for six weeks, Reagan said, "I still remain optimistic that the solution is going to be found.

"I don't comment on specifics because I know how sensitive these negotiations are," the president said. ". . . So I can't go beyond that except to say that unless and until Ambassador Habib would tell me that there's nothing more to be negotiated and he can't solve it, I'm going to continue to be optimistic."

Questions about Lebanon dominated the foreign policy aspects of the news conference, in which Reagan also discussed the U.S. dispute with Western Europe over the Soviet natural-gas pipeline, the administration's certification of human rights progress in El Salvador and the prospects for a summit meeting with Soviet President Leonid I. Brezhnev.

Reagan said he had "no second thoughts" about his decision to deny American technology to West European firms supplying equipment for the pipeline that will carry gas from Siberia to Western Europe.

Asked whether this move were inconsistent with U.S. grain sales to the Soviets, the president contended that, in seeking ways of influencing Moscow to ease repression in Poland, the United States would hit home much harder with pipeline sanctions than by reinstituting a U.S. grain embargo.

"The technology for the pipeline is mainly only obtainable from the United States. Grain the Soviet Union can get in other places if they want it. So we wouldn't be achieving very much if we had used that as it was used back a couple of years ago. . . . It didn't hurt the Soviet Union, but it was a terrible economic blow to our farmers."

He also contended "that grain will result in the Soviet Union having to pay out hard cash, and they're not too flush with that right now. The pipeline, when finished, will result in the Soviet Union getting hard cash which it does not now have and which it can then use to further build up its military might."

Reagan is expected to announce shortly a one-year extension of the existing U.S. grain-sale agreement with the Soviets.

He argued that U.S. relations with European allies remain strong despite the acrimony generated by the pipeline dispute. "This is kind of like a fight inside a family, but the family is still a family," he said.

The president defended his administration's controversial move in certifying Tuesday that the U.S.-backed government in El Salvador is making progress on human rights and other reforms and thus is eligible for continued U.S. military assistance.

Conceding that some rights abuses still exist there, Reagan said: "I'm quite sure that there are unfortunate things that are going on and that are happening. The idea is, are they the Salvadoran government legitimately and in good faith making progress in trying to solve that--resolve that."

Asked about his previous statement that a summit with Brezhnev was "in the works," Reagan responded, "I don't know whether it's going to be this year or next or at all. . . . It takes two to tango.

"A summit isn't the answer or the cure for everything that's wrong in the world," Reagan said. "There have been no positive replies or steps. . . . If at such time we know that there is an agenda and there is a real purpose in having this, we'll have a summit."

He also said that while his administration wanted to continue good relations with China, he would not bow to pressure from Peking to stop providing Taiwan with defensive arms. "It's a moral obligation, and we'll carry it out," he said of commitments to Taiwan.

In his comments on the Middle East, Reagan reiterated that the United States would view as "a step forward" recognition by the PLO of Israel's right to exist and those U.N. Security Council resolutions that form the framework for efforts to resolve the Arab-Israeli conflict.

"Then I would feel that the United States could enter into discussions with the PLO," he added in indirect reference to speculation about U.S. recognition of the PLO. "I'm not speaking for Israel. That's up to them, and we could not speak for them."