Jordan and Syria, ending two days of reconciliation talks today, announced agreement to reactivate a once-influential political coordinating committee and pledged to work toward "joint Arab action" in the Middle East peace process.

Jordanian Prime Minister Zaid Rifai returned to Amman after a 24-hour visit to Damascus, where he achieved what observers called a significant breakthrough in improving relations between the two countries. Relations had been strained since 1978, with Syria accusing Jordan of aiding opposition factions and the two sides differing on a variety of regional issues.

There has been widespread speculation that Rifai's visit was also intended to prepare for a meeting between King Hussein of Jordan and Syrian President Hafez Assad, but the joint communique released today made no mention of such a meeting.

The communique also did not mention the Palestine Liberation Organization -- the center of a key policy difference between the two countries -- or the agreement reached between Hussein and PLO leader Yasser Arafat last February for joint Middle East peace efforts.

Syria has opposed Arafat's leadership of the PLO and has backed rival factions, but the communique gave no indication whether the two governments reached any understanding on the issue.

The Supreme Joint Committee to Coordinate Cooperation, which is to be revived, was formed in 1975 after a visit by Assad to Amman. When relations were at their height, it met twice a month under the two countries' prime ministers to map out joint political and economic policies.

Although the communique indicated that the committee is being revived to achieve economic coordination and to lift the trade restrictions that have been in effect for the past five years, Rifai's visit also considerably narrowed the political gap between Amman and Damascus on the Middle East peace process.

During a seven-hour meeting between Assad and Rifai, the two sides agreed "on the necessity of enhancing joint Arab action in all fields to achieve a just, comprehensive and durable Middle East peace, and to confront Israeli aggression," the statement said.

Its reference to the peace process, observers said, indicated that Jordan has succeeded in convincing Syria that it is not about to embark on a unilateral course of direct negotiations with Israel, and that it is serious in calling for an international format for peace talks that would include all the parties to the conflict.

"The two sides affirmed their rejection of partial and unilateral solutions, and emphasized that just, comprehensive and durable peace cannot be achieved without the convening of a U.N.-sponsored conference to be attended by all the parties to the conflict," the statement said.

The two sides also called for participation by the Soviet Union and the United States in the peace process. But Jordan's call, maintained until recently, for the inclusion of the other three permanent U.N. Security Council members -- Britain, France and China -- in the peace process was omitted from the statement.

Although Jordan has consistently affirmed its rejection of direct negotiation with Israel in favor of an international peace conference, its plan for such a format envisages breaking up the conference into Arab-Israeli committees, with each committee discussing one aspect of the conflict. This, Jordanian officials argue, would amount to direct negotiations within an international framework.

Meanwhile, Los Angeles Mayor Tom Bradley arrived in Amman and said he would deliver a message to Hussein on Thursday from Israeli Prime Minister Shimon Peres.

Bradley said he hoped his meeting with Hussein would result in "some clue from King Hussein as to what the prospect may be for him and Peres to continue their peace initiatives." He would not divulge the contents of Peres' message to Hussein, saying it was "personal."

Bradley, who is to return to Israel Thursday, said he felt that both Hussein and Peres "have clearly made out some guidelines that are acceptable to both of them, that would in my judgment lead to meaningful negotiations toward peace."

Wat Cluverius, recently appointed an aide to Assistant Secretary of State Richard Murphy, also arrived here today on a mission related to the peace process. His arrival was not mentioned by the Jordanian state-run media, however, and U.S. Embassy officials refused to give any details about his activities here.

Arafat also is here and is to meet with Amman-based Palestinian officials Thursday. There were no indications whether Arafat will meet with Hussein on this visit.