The Kremlin is hoping that the recently announced Arab peace plan for the Middle East will help sink a US negotiating initiative that would exclude the Soviets.
At the same time, the Soviets appear concerned that key Arab leaders may ultimately try the road charted by President Reagan in his Mideast policy address of some two weeks ago.
The Arab plan, emerging from a summit conference in Morocco, stakes out some potentially common ground with the US approach on the question of recognizing Israel's right to exist but differs with the Americans on various points, including establishment of a full-fledged Palestinian state.
The official Soviet news media have moved quickly to underscore the differences between the Arab and US approaches on Palestinian statehood, something Moscow has long supported but the Reagan plan would exclude. The Soviets are also playing up their ties with the Palestine Liberation Organization, with which the American government has ruled out direct contact.
Soviet President Leonid Brezhnev in effect joined his media's campaign in a message to PLO chairman Yasser Arafat that was released here Sept. 14.
Charging that Washington, as Israel's key foreign arms supplier, must share ''responsibility for the tragedy in Lebanon,'' Mr. Brezhnev added: ''Today, too, the United States is trying to deny the Palestinians their sacred right to self-determination and to establishing their own state.
''In this hour of trial, I confirm anew that the Soviet Union was, and remains, on the side of the Arab people of Palestine and their only legitimate representative, the PLO.''
Foreign diplomats here interpret the speed with which Moscow has moved to emphasize the ''anti-Arab'' character of the US initiative - and to focus on those features of the Arab plan in variance with it - as partly reflecting Soviet concern over the position taken by some Arab leaders on the Reagan move.
The Soviet response has preceded a definitive ruling on the US proposals from Mr. Arafat. Jordan's King Hussein, increasingly critical of US policy in recent years, is taking a decidedly friendlier tack toward the Reagan initiative. The Egyptians seem to envisage a marriage of the Arab peace plan to the ideas of Mr. Reagan, benefiting from the theoretical US ability to deliver Israeli acceptance of a workable compromise. (Or so, at least, says the Soviet news agency of the Egyptian position, in a commentary concluding that Washington has given no sign it ''will pressure Israel in any way in the interests of the Arabs.'')
On balance, most diplomats here maintain, the summit in Morocco turned out better for Moscow than it might have. The Arabs' move toward recognizing Israel's right to exist, a key US policy goal, was an acrobatically inexplicit one that would not seem to promise early Mideast entente. The Arab peace plan envisages a guarantor's role for the United Nations, which, for the Soviets, is at least some improvement over a virtual US monopoly on Arab-Israeli diplomacy. And the Arabs' declared vision of a Palestinian state, coupled with side demands like the dismantling of Israeli settlements on the West Bank, is in concert with stated Soviet policy and in contradiction with that of the Americans.
The fundamental concern here, diplomats sense, is that the Reagan plan has served to encourage a feeling long prevailing among wide circles of Arab opinion that Washington offers the best bet for any palatable negotiated settlement, and that diplomatic activity may indeed center on efforts to graft the summit peace plan to Mr. Reagan's initiative.