Palestine Liberation Organization chairman Yasser Arafat said today after four days of talks with Jordan's King Hussein that further negotiations are necessary on plans for a possible future Palestinian federation with Jordan.

Jordanian sources acknowledged before Arafat's comments at a press conference tonight that the talks had produced few tangible results, although both sides said they were friendly. Beyond that, Arafat's refusal to rule out federation with Jordan was seen by diplomats here as possibly giving the king the diplomatic maneuvering room he needs to continue to pursue President Reagan's peace initiative, which calls for some form of linkage.

The PLO feels that Hussein can play a useful role in "explaining" to the United States the positions taken by Arafat during his talks here, an adviser to the guerrilla leader said.

Another source familiar with the negotiations said that Hussein would have to be content in public with a PLO spokesman's statement yesterday that the PLO was willing to consider entering a federation with Jordan but that a Palestinian state must be created first.

Arafat himself declined to rule out some form of linkage between Jordan and a Palestinian entity to be created on the West Bank and Gaza Strip following Israeli withdrawal from those territories in a comprehensive Middle East peace settlement. But in an apparent sign that he is concerned about lack of support from more radical elements of the PLO and the Syrian government, he said that the Palestine National Council, or parliament in exile, would have to approve any such links with Jordan rather than he alone.

"It's not for me to accept or reject," Arafat told journalists at the guest residence where he has stayed during his visit here. "I have to go back to my council."

PLO officials said that the talks with Hussein -- four sessions totaling 12 hours since Sunday -- were over and that Arafat would leave Wednesday for Tunis where he is scheduled to meet French Foreign Minister Claude Cheysson.

The sessions were aimed at achieving a consensus on the future of the occupied territories if Israel could be convinced to withdraw. In the context of current Middle East diplomacy, the question was whether the PLO would yield enough to demonstrate to the United States that the Palestinians were sufficiently flexible to make possible progress under Reagan's peace initiative.

Reagan's plan calls for occupied territories to be "associated" with Jordan rather than becoming an independent Palestinian state as the PLO demands.

Arafat criticized the Reagan plan for "neglecting" to endorse an independent Palestinian state and the authority of the PLO to represent the Palestinian people. He added, however, that he saw "some positive elements" that should be discussed by a follow-up committee named by the recent Arab summit at Fez, Morocco.

The question of whether the PLO and Jordan can agree on a formula on the eventual future status of the occupied territories now will be assigned to a joint Jordanian-Palestinian committee that was established in 1978 to funnel Arab aid money into the West Bank and Gaza Strip, Arafat said. The committee is made up of high-ranking officials from both sides, including members of the 15-man PLO executive committee.

PLO officials did not sound as though it would complete its work any time soon. Nabil Shaath, a senior official, said that the main accomplishment here was "the cementing of trust" between the PLO and Jordan after years of mutual recriminations.

Jordanian officials also praised the warm climate of the talks but stressed that Hussein's only victory was the PLO's acknowledgement that a possibility existed for a federation. Hussein himself proposed a federation in a speech Sept. 20, three weeks after Reagan announced his initiative. It was similar to an idea he had proposed in 1972 that the PLO rejected at the time.

There was no public sign of progress on the other major front where the PLO could have made concessions: recognition of Israel's right to exist within its frontiers before the 1967 war.

Arafat said the issue was not raised, but Jordanian sources said the king was seeking a more open recognition by the PLO than provided in the Fez resolutions.

Arafat himself suggested that he was sticking to the wording of the Fez resolutions -- which call on the United Nations to guarantee the security of all states in the region but do not explicitly refer to Israel. When asked if the clause meant that Israel should have the right to exist, Arafat said he understood it "the way it is written."

Both PLO and Jordanian officials suggested that the king and Arafat may have achieved more in their hours of private sessions than they were willing to make public at present. "A long period of silence," as one Jordanian source put it, could allow both sides a chance to deal with their respective political and diplomatic problems.

Arafat could use some time to seek to shore up his support with the more radical, particularly pro-Syrian elements, in the PLO who are dissatisfied over his rapprochement with Jordan. Arafat declined to respond to questions about a statement by Syrian Information Minister Ahmed Iskandar Ahmed Sunday questioning his right to speak in negotiations with Hussein without a full mandate from the executive committee. Arafat said he had requested a full text of the Syrian statement so that "the entire executive committee" could consider it.

Any formal moves toward endorsing federation with Jordan or recognizing Israel more explicitly would have to be approved by the full executive committee and the Palestine National Council. The 350-member council is expected to meet within about a month.

Hussein, meanwhile, can test the waters with the United States to find out how receptive it is to a PLO that at least has not yet ruled out Reagan's peace initiative. PLO officials stressed repeatedly that they would like to see Reagan start to put his plan in effect, meaning that he should try to get the Israelis to withdraw from the occupied territories.

When pressed for a description of what Reagan could do, one high-ranking PLO official said privately that the U.S. should start putting pressure on Israel to commit itself to be willing to withdraw from occupied territories in exchange for guarantees of peace.