Beirut — The talks would have been unthinkable only months ago. Palestinian leader Yasser Arafat and Jordan's King Hussein, once the most bitter enemies, sitting together in the Jordanian capital to discuss possible confederation between Jordan and a future Palestinian entity.
Spurred by rapidly changing circumstances, both Hussein and Arafat are eager to act - but neither can do it alone.
The Jordanian monarch has the ear of the United States. The chief of the Palestine Liberation Organization has the Arab negotiating mantle. So the two are attempting to fashion a joint approach to President Reagan's peace initiative.
Paving the way for this meeting of former enemies has been a series of basic changes in the Middle East equation:
* The PLO was forced out of its main base - Beirut and south Lebanon - by the Israeli invasion. Thousands of exiled Palestinian fighters are virtually quarantined in various Arab countries. And Israel continues its de facto annexation of the occupied West Bank and Gaza Strip - the Palestinians' last hope for a state.
* The United States, embarrassed by the Israeli invasion, on Sept. 1 finally put forth a concrete set of Mideast peace proposals. True, the plan does not mention the PLO (which the US will not recognize until the PLO recognizes Israel) and opposes an independent Palestinian state. But the proposals do support Palestinian self-government on the West Bank in association with Jordan and stress the return of Israeli-occupied land. This is the strongest position taken by the Reagan administration so far.
* Moderate Arab states at the Fez summit in Morocco, fearful of Israel's unbridled military power and of future Mideast radical upheavals, left the way open for the American approach, even while officially endorsing the PLO and an independent Palestinian state. A high-level Arab delegation led by King Hassan II of Morocco will visit with President Reagan in Washington later this month to explore the possibility of US-PLO dialogue.
* Jordan has reacted enthusiastically to the Reagan proposals. It is worried by Israeli insistence that its truncated east bank kingdom is the de facto Palestinian state and by Israeli Defense Minister Ariel Sharon's hints that he might effect this transformation by force. Disappointed by the Fez summit, which left the PLO with the mantle for negotiations over the West Bank, King Hussein has sought to coordinate a joint negotiating strategy with the PLO. Any such strategy is likely to put US intentions to the test.
* Syria, now the PLO's main base and a potential spoiler in a PLO-Jordanian dialogue, is looking to the US to ensure Israeli troop withdrawal from Lebanon. It also wants the US to revive pressure for return of the Israeli-annexed Golan Heights. Syria is anxious to withdraw its 30,000 man peace-keeping force from Lebanon after severe losses during the Israeli invasion. An indication of US backing on the Golan issue - beyond the hint contained within the Reagan proposals - could soften Syria's antagonistic attitude tothe Reagan plan and further encourage its diplomatic thaw with the US.
After three days of Hussein-Arafat meetings, PLO spokesman Mahmoud Labadi said in Amman Oct. 12 that the PLO was ready to negotiate with Washington on the basis of the Reagan proposals, because the Americans were the only ones to pressure Israel into withdrawing from the occupied territories.
This is the first time the PLO has shown interest in the Reagan plan. It is big step, since the plan does not specify an independent Palestinian state.
While no official details of a PLO-Jordanian agreement have yet emerged, the independent Lebanese magazine an-Nahar International said this weekend that Arafat was expected to conclude a secret pact in which Hussein would be granted some kind of limited power to negotiate the future of the West Bank and Gaza Strip on the behalf of the Palestinians. Well-informed Palestinian sources in Amman told the Monitor last month that should Hussein obtain US assurances of the return of the West Bank, Gaza, and Arab east Jerusalem (admittedly unlikely) , the PLO had already given him carte blanche to negotiate.
In discussing a formula for future consideration, the PLO and Hussein must overcome a legacy of mutual mistrust dating back to 1970, when the King expelled the PLO. Last week, Hussein pardoned more than 700 Palestinian fighters involved in the 1970 conflict.
PLO spokesman Labadi, no doubt mindful of this mutual distrust, told reporters in Amman Oct. 11 that an independent Palestinian state on the West Bank and Gaza must precede federation.
''Our basic aim,'' he said, ''is to secure an Israeli withdrawal, get Israel to recognize our right of self-determination, set up a Palestinian state on the returned territory, and then talk of a federation or association with Jordan.''
In a BBC television interview Sept. 13, the King spoke of a Palestinian-Jordanian federation with a joint defense and foreign policy.
The independent Kuwaiti daily Al-Qabas Oct. 11 quoted unidentified ''informed sources in Amman'' as suggesting that the proposed confederation would comprise two separate entities under a single government with separate passports and separate armies under a single command. Reports Tuesday from Amman said a dispute had arisen over the PLO's wish to have Jerusalem as a capital. The King wanted Amman.
King Hussein proposed in his BBC interview that the ''framework for our future relations, Palestinian and Jordanian,'' be submitted to both Palestinians and Jordanians in a referendum ''at an appropriate moment.'' Senior Jordanian sources told the Monitor that Arafat had already agreed to such a referendum.
But details of a federation remain very premature. Even should Jordan and the PLO produce such a plan and a joint negotiating strategy acceptable to the US, Israel has stated firmly that it will never relinquish sovereignty over the West Bank, Gaza, and Jerusalem. Even Israeli Labor Party opposition leader Shimon Peres would insist on retaining substantial chunks of the West Bank along with Jerusalem. Hussein has said he will not hold peace talks as long as Prime Minister Menachem Begin is in office. Rather he seems focused on gaining stronger US backing for Arab positions.
Moreover, Arafat is already feeling pressure from Syria and from several more radical, Damascus-based factions within the PLO. Syrian Information Minister Ahmed Iskandar told the New York Times that Arafat could not speak in Amman for the PLO executive committee ''when he has no mandate from it.''
Syria is anxious not to lose influence over PLO diplomatic moves and Syrian-backed PLO No. 2 man Abu Iyad (Salah Khalaf) has opposed King Hussein's federation plan.