Chances for reviving the Reagan Mideast peace initiative, slim at best, appear to hinge on some dramatic new United States move. And this probably means confronting the Palestinian issue head on.
King Hussein of Jordan, on whom the US had counted to enter peace talks with Israel over the future of the Israeli-occupied West Bank and Gaza, has now firmly removed himself from the action. He believes Jordanian efforts to win Arab and Palestinian support for such negotiations have reached a dead end.
The King, who spoke twice by telephone with President Reagan on Sunday, believes that it is up to the Americans to decide what new steps to take.
But authoritative Jordanian sources say the King doubts that the peace process can be revived unless the US redefines its proposals to include the Palestinian right to self-determination - or unless the Palestine Liberation Organization modifies its demands.
The Reagan proposals, issued Sept. 1, called for a return of Israeli-occupied land, which would then become a Palestinian entity linked to Jordan. The plan did not call for an independent Palestinian state and did not mention Palestinian self-determination. Nor did it provide a role for the PLO. The US has said it will deal directly with the PLO only if that organization recognizes Israel's right to exist and United Nations Resolutions 242 and 338.
The US had hoped that Jordan would bring Palestinian representatives to the bargaining table in a joint Jordanian/non-PLO Palestinian team. But Jordan, bound by the Rabat Arab summit resolution of 1974 that recognized the PLO as the sole representative of the Palestinians, first wanted public PLO approval.
For six months, the PLO and Jordan sought to work out a formula that could win an Arab consensus and provide a basis for a possible joint Palestinian-Jordanian negotiating team. But these efforts came to a dead end last week. The King finally abandoned efforts to enter US-sponsored peace talks.
Having made what he considered to be every possible effort, King Hussein is said to believe that other involved parties - the United States, the PLO, and the Arab states - must now bear the burden of finding a peace formula.
The next few weeks are seen here as a period of reappraisal of positions by all sides.
Authoritative Jordanian sources say it is not clear whether an Arab summit scheduled for April 16 in Fez, Morroco, will still take place unless a common basis can be found beforehand.
The questions now are what US steps would be necessary from the Arab perspective to revive the peace process, and whether the US will want to take them. American officials expect no changes in US policy.
Senior Jordanian sources say if the peace process fails totally, the outcome will be disastrous for the Middle East and for US interests there. ''You won't be able to be pro-American in your living room,'' said one Jordanian official.
The King is said to believe that US failure to gain a withdrawal of Israeli troops from Lebanon has greatly damaged US credibility as a mediator in any future negotiations over the West Bank. (Senior US officials told the King withdrawal would begin last December.)
The same holds true for US failure to halt Israeli settlements on the occupied West Bank, despite periodic critical US statements on the settlements.
However, even if dramatic movements were made by the US on either of these issues, authoritative Jordanian sources believe it is too late to affect the Jordanian decision to quit the process. They believe the other parties concerned will have to figure a way around the current impasse.
With Jordan removed from the negotiating process, the buffer between the US and the PLO also disappears. Senior PLO leaders, like number No. 2 Salah Khalaf (Abu Iyad), have specifically stated that if the word ''self-determination'' were added to the Reagan plan, it would be acceptable to the PLO.
But the US opposes this, believing it would guarantee Israeli refusal to negotiate. Moreover, with an election year approaching, the Reagan administration will have to decide what kind of domestic political risks it is willing to take over its Mideast policy, and whether it wants to cut its losses or to pursue a process that may dramatically increase its risks.
The PLO, too, has a problem. By bowing out, Jordan has indicated that in the future, Palestinians from the occupied territories must take their problems to the PLO, and presumably blame that organization if their situation remains difficult.
To refuse to press toward negotiations may cost the PLO much of its constituency in the long run. But it appears unlikely that if the PLO did not modify its demands in favor of the Jordanian proposals, it would do so for the Americans. Thus the PLO issue, which the Reagan plan attempted to finesse, may come back to haunt it in the end.