Yasser Arafat said yesterday that "the door is still open" for new talks between the Palestine Liberation Organization and Jordan toward a Middle East peace agreement and that Arab diplomatic efforts are under way to "reduce the obstacles" between him and Jordan's King Hussein.

The PLO chairman, making an unexpected visit to Bulgaria just five days after the collapse of Hussein's efforts to win Palestinian approval to engage in American-sponsored peace talks with Israel, was quoted by Wafa, the official PLO news agency, as saying that a new Arab summit meeting on the issue would be held in two weeks.

Arafat left Sofia, the capital of Bulgaria, for an undisclosed destination late last night, according to BTA, the official Bulgarian news agency.

The summit, originally planned for this weekend but called off after the breakdown of the PLO-Jordanian talks, had been postponed "to complete discussions and efforts to ensure its success," Arafat said, according to Wafa.

The State Department had no official reaction to Arafat's statements, but U.S. sources said they fit in with other "positive sounds" in recent days that are seen as keeping alive President Reagan's Middle East peace initiative, which counted heavily on Hussein's gaining approval of the PLO to negotiate on behalf of Palestinians.

Hussein broke off talks with Arafat on Sunday, accusing the PLO leader of reneging on an agreement to take part in peace talks on the basis of the U.S. plan.

On Monday, in North Yemen, Arafat called for "continuing the constructive, fraternal dialogue with Jordan," but Jordan, in public at least, has shown no eagerness for a resumption of the talks.

The seven-page Jordanian communique announcing the end of the talks gave no indication of an "open door" to their resumption and said only that Jordan would "support the PLO within our capabilities." Jordanian officials, showing what some observers saw as a calculated reluctance, indicated later that they were willing to renew negotiations, but only if there were assurances of reaching a firm agreement.

The Wafa account of Arafat's press conference in Sofia gave no details of the "Arab efforts to reduce the obstacles that appeared at the last meeting," which the PLO leader said were under way. Morocco's King Hassan, however, has been contacting Arab leaders in an effort to prevent what one observer called a "full breakdown in dialogue" between Jordan and the PLO.

Arafat also restated his support of the Soviet call for an "international conference to arrive at a lasting comprehensive solution in the Middle East," a rival to the U.S. peace proposal that had not been prominently mentioned in some time.

American sources noted, however, that this has long been a PLO position, and its restatement was to be expected in Arafat's visit to the capital of the Soviet Union's closest ally.

PLO and other accounts of Arafat's trip to Bulgaria have given no indication of its purpose. It had not been announced until Arafat suddenly left Tunis on Thursday after abruptly postponing a meeting of the PLO's executive committee planned for that day to review Palestinian-Jordanian relations. The meeting now is expected to take place this weekend.

Wafa accounts of Arafat's brief visit in Sofia said only that he held a round of official talks with Bulgarian leaders, including Communist Party chief Todor Zhivkov, and "gave a review of the political situation and Arab and international developments in the Palestinian question."

Arafat reportedly told Zhivkov that the PLO "is now conducting the fiercest struggle to preserve the unity of the Arab position" on the Mideast.

There was speculation here that Sofia, well out of the international limelight, could provide an unobtrusive site for a meeting between Arafat and Soviet leaders. But there was no evidence such talks are taking place.

Wire services reported the following Middle East developments:

U.S. envoy Philip Habib met Israeli Prime Minister Menachem Begin in stepped-up negotiations on foreign troop withdrawals from Lebanon, but reports from Beirut discouraged speculation that an agreement was near.

Habib's talks in Jerusalem covered Lebanon's response to Israeli demands for security arrangements in southern Lebanon when Israeli forces withdraw, Israel radio said.

A senior Lebanese official, who asked not to be identified, said at a briefing in Beirut that Israel is demanding to keep 200 troops in Lebanon to help patrol the south of the country after the rest of its invasion force withdraws.