Palestine Liberation Organization Chairman Yasser Arafat voiced urgent concern today over what he described as Israeli-instigated disturbances and violence on the West Bank, but he and key advisers indicated that the tensions there would not cause them to rush into unqualified acceptance of President Reagan's Middle East peace proposal.

Arafat, who is here for talks with Jordan's King Hussein on the Reagan plan, indicated in a press conference that he would continue to insist on recognition of the PLO as the sole legitimate representative of the Palestinians and would act only in peace initiatives within the framework of an Arab consensus.

He cited the recent wave of complaints of mysterious illness among Arab schoolgirls on the West Bank and attacks on Arabs by Jewish settlers as evidence of "the genocide against the Palestinian people."

While Israeli officials say they have found no indication of poisoning in the sickness complaints, the PLO and its news service, Wafa, have repeatedly charged that the Jewish state is poisoning and harassing Arabs to get them to leave the West Bank.

"The major reason for all these crimes is an attempt to scare our people in the occupied territories," Arafat said. "I plead to all people, to all tolerant people in the world to stop these crimes. And I especially plead and address my words to those honorable people in Israel who really spoke about the crimes that were perpetrated against our people in Sabra and Shatila." He was referring to the demonstrations in Israel following the massacre of Palestinians at two Beirut refugee camps last September.

Arafat, sending out confusing signals, did not reject Reagan's initiative outright today, but when asked if he believed it had any future, he said, "That depends upon the attitude of President Reagan himself."

The PLO chairman brought up the fact that Reagan had said last week that the sale of F16 fighters to Israel would be delayed until Israel withdrew from Lebanon. But Arafat noted that the United States had agreed recently to provide additional Sidewinder air-to-air missiles to Israel.

"It's still the Americans completely supporting . . . this Israeli aggression, this Israeli military junta," Arafat said.

Hussein and Arafat met again today for two hours. An Arafat aide said that PLO Executive Committee members would come here from Syria Monday to participate in discussions related to the talks.

Arafat arrived here on Thursday for talks with Hussein on Reagan's initiative that are regarded as critical. According to diplomats and Hussein's advisers, the king regards Arafat's support as essential to entering negotiations for the creation of a Palestinian entity on the West Bank and Gaza in association with Jordan as called for in the Reagan plan.

Apparently because of anticipated Israeli objections, the Reagan plan specifically rules out creation of an independent Palestinian state and direct dealings with the PLO as representative of the Palestinians, which are called for in the Fez summit proposal by Arab states last September.

"I am still committed to what the Arabs accepted," Arafat said today. But he did not rule out absolutely a future bridge between the two proposals.

Arafat called for a new Arab League summit "where everything will be decided," United Press International reported.

He and his advisers, however, seemed anxious to convey an image of strength, steadfastness and courage despite the expressions of concern over the problems on the West Bank.

"We are looking at the whole problem," said an Arafat deputy, Khalil Wazir, also known as Abu Jihad. "We can't say that time is the only matter or fact."

The PLO's senior foreign affairs official, Farouk Kaddoumi, seemed to reject Reagan's plan out of hand following Arafat's news conference. He called instead for U.N.-sponsored peace negotiations including the United States and the Soviet Union.

But Wazir was less unyielding, although he, too, said the U.S. proposal did not go far enough to satisfy "Palestinians aims." He said that "we are speaking to all those who can speak to the Americans" to intercede on behalf of the Palestinian position.

"The Palestinians are not going to give a mandate to anyone," Wazir said. "There was a long struggle for sole representation. We are not going to allow anyone to speak for us."

Egypt's President Hosni Mubarak, at the end of a three-day official visit to Peking, urged the Palestinians to let Jordan represent them in negotiations with Israel over the future of the West Bank and the Gaza Strip, United Press International reported.

"If the Palestinians and the Jordanians don't reach an agreement with regard to their relations, then people will criticize the Arabs for not promoting peace," Mubarak told a news conference. "We must not lose this golden chance for peace in the Middle East."