As U.S. special envoy Philip C. Habib's revived Middle East peace-making mission inched toward an apparently inconclusive end, a Soviet counterpart concluded his own discreet regional tour today to promote Soviet participation in the peace process.

With Habib going a second round in talks in Israel with Foreign Minister Yitzhak Shamir, special Soviet envoy Mikhail Sytenko spent 24 hours here for talks with Palestine Liberation Organization Chairman Yasser Arafat and Lebanese President Elias Sarkis to wind up a four-nation Arab tour. He has been lobbying for Soviet President Leonid Brezhnev's proposal for an international conference on the Middle East.

Sytenko declined to comment on the coincidence of his trip to Morocco, Jordan, Syria and Lebanon with Habib's mission.

The timing of Sytenko's trip was also interpreted by Arab analysts and diplomats as a clear effort by the Soviet Union to capitalize on the setback at the Arab summit last month of Saudi Arabian Crown Prince Fahd's plan for a common Arab effort for a comprehensive Middle East peace settlement.

Sytenko told reporters here that his three-hour meeting with Arafat Sunday night and his shorter meeting with Sarkis this morning were part of a general "exchange of views."

The Soviet roving ambassador noted that Brezhnev had already launched a Soviet plan for a Middle East settlement last February with his proposal for an international conference at which both Israel and the PLO would be represented as equal parties and whose final settlement would be guaranteed by both the United States and the Soviet Union.

The Brezhnev plan has received little attention, mostly because of determined resistance to any Soviet role in peace negotiations by the United States, Israel, Egypt and such Arab moderates as Saudi Arabia.

One of the points raised by radical Arab states in scuttling the Saudis' eight-point peace initiative at the 12th Arab summit at Fez, Morocco, was the lack of provision for Soviet participation. The PLO and such Soviet allies in the Middle East as Syria have insisted that no true settlement can be reached in the Middle East unless both superpowers are involved in the final settlement.

PLO officials here, including many moderates who had been prepared to go along with a good part of the Fahd plan -- although not its implied recognition of Israel at this stage -- are adamant that no settlement can be reached through the good offices of one or two Arab states, but must be a part of an overall agreement among Arabs that could best be brought about in the sort of international conference proposed by the Soviets.

Sytenko's reaffirmation to Arafat of "the Soviet Union's continued support for the Palestinian people's just struggle" and for their "establishment of an independent state" made clear why Soviet involvement in the peace process appeals to the PLO.

This is so even while the PLO leadership is aware that in dealing with Israel only the United States, whose recognition they are seeking, has the clout to produce the sort of compromise that could lead to a real Middle East peace treaty.

After meeting with Sarkis, Sytenko flew back to Moscow. Habib is expected back here tonight or Tuesday for his own meeting with Sarkis.

The stated purpose of Habib's trip this time is to try to reinforce the fragile cease-fire between Israel and the PLO in southern Lebanon that he helped negotiate through the good offices of Saudi Arabia last summer. The cease-fire has remained precarious because of Israeli concern over PLO guerrilla concentrations in southern Lebanon and the continued presence of Syrian surface-to-air antiaicraft missiles in Lebanon's Bekaa Valley.

Habib has refused to comment on his discussions in Lebanon, Syria, Jordan, Saudi Arabia and Israel, and there have been few signs that he is making headway.

Syria has denounced his mission as a smokescreen to distract Arabs from the agreement on strategic cooperation between the United States and Israel. Official Syrian newspapers have insisted that the missiles in Lebanon are "not negotiable."

On the other side, Israeli Foreign Ministry spokesman Avi Pazner said after Habib's second meeting with Shamir today that "his mission was to solve the problems of the region. For the time being the problems have not been solved.