Jordan's King Hussein warned today that U.S. congressional action to delay or block a $1.9 billion arms sale to Jordan could badly damage Washington's credibility in the peace process instead of helping to push it forward.

Hussein, at the center of the latest round of tentative Middle East peace maneuvers, spoke sharply about the congressional move to delay further consideration of the arms sale until March 1 unless Jordan begins direct peace negotiations with Israel before then. That measure passed the Senate today by a vote of 97 to 1.

The king, speaking to American reporters this morning, said this action amounted to "blackmail" at a moment he called a "very serious crossroads" in the search for a Middle East settlement.

Hussein spent several hours today in consultation with Egyptian President Hosni Mubarak, who heads the only Arab government formally at peace with Israel. Neither leader would comment afterward on their discussion, but aides said before the meeting that it was aimed at coordinating efforts to respond to an initiative by Israeli Prime Minister Shimon Peres at the United Nations on Monday.

Hussein warmly embraced Peres' address as "a very fine speech" and a "positive contribution." He cited as "positive developments" Peres' willingness to contemplate an international peace conference and the U.N. involvement that Jordan seeks. Israel previously had opposed such measures.

Hussein insisted on his belief that the best hope for a lasting peace is to be found through an international forum under U.N. auspices. "The only place where Jordan and Israel will have direct negotiations will be within the context of an international conference," he said.

Peres put strong emphasis Monday on his call for an immediate end to the official state of war between Israel and Jordan that has existed since 1948.

Hussein said today this seemed to contradict other parts of the Peres address that were "talking about a comprehensive settlement, meaning all the states in the area -- all the parties to the conflict, one would assume."

But Hussein also said that while an international conference "will have to oversee and partake in arranging the negotiations," it is "fairly obvious" that the negotiations that follow "will take place directly between the parties involved."

He praised Peres as a man who shares "the same objectives" as he does: the safety and security of future generations in "the entire area."

Hussein suggested that Peres is opposed "to the views of the extremists that are openly supported by actions threatening the very possibility of attaining that goal."

Although the king was speaking of extremists in Israel, he also talked in sharp terms about his own troublesome ally in the peace process, the Palestine Liberation Organization.

Hussein did not suggest that the Feb. 11 accord with PLO Chairman Yasser Arafat for a joint approach to peace might be discarded. He made it clear that he still has no intention of moving toward peace with Israel unless he has broad Palestinian support.

But since the Achille Lauro cruise ship affair and an aborted meeting between a joint Jordanian-PLO delegation and Britain's foreign secretary -- for which Hussein blames the PLO -- the king said he is "not very happy with the situation" and "we are at the point of reassessment."

"I think we can do a lot to assist the PLO, but the PLO can do a lot to assist itself and assist us," Hussein said. He added that he expects to have "a very, very frank discussion" with Arafat when the PLO leader comes here, probably next week.

A western diplomat who consults closely with Hussein said he is likely to "read Arafat a bill of particulars," pushing the PLO leader to take a clearer stand embracing peaceful negotiations and rejecting the kind of violence in the name of "armed struggle" that seriously damaged the process in recent weeks.

Hussein continued to describe the PLO as "the sole legitimate representative of the Palestinian people." It has been recognized formally as such by the Arab world since 1974.

But Hussein added, "I hope they live up to their great responsibilities in that regard."

Hussein's apparent warmth toward the Israeli prime minister and his chilly remarks about Arafat indicate the king may already be moving quickly in a direction that could bring him together with Peres for talks once the "international context" is agreed upon.

Hussein made it clear today, however, that U.S. congressional efforts to link the sale of American arms to his willingness to start such direct talks will only set back the cause of peace.

Through three decades of close relations with Washington, Hussein's own credibility in the region has been tied to that of the United States.

Obviously stung by news of the Senate setback, Hussein warned that postponement of the sale would force the conclusion that there is no longer any substance to claim that Washington is "even-handed" in dealings between Israel and Washington's Arab friends.

"We might have arrived at that conclusion a long time ago," Hussein said, "but this will finally make it abundantly clear that the United States by adopting such a position has damaged its own credibility."

"You can't commit yourself to something and then back away from it and expect us to accept your commitment toward something else," he said.

Staff writer John Goshko reported from Washington:

Assistant Secretary of State Richard W. Murphy secretly visited Amman this week to confer with Hussein about Peres' proposals, but U.S. officials and diplomatic sources said Murphy's mission apparently failed to achieve any dramatic breakthrough toward direct Israeli-Jordanian peace talks.

State Department spokesman Charles Redman disclosed the trip only as Murphy, the administration's chief Middle East troubleshooter, was en route to New York to report to Secretary of State George P. Shultz.

Other officials and diplomatic sources, speaking on condition that they not be identified, said Murphy's purpose was to sound out Hussein's attitude toward Peres' call Monday for direct negotiations under international auspices with Palestinian participation in the Jordanian negotiating team.

Specifically, these sources said, Murphy sought to ascertain whether Hussein is willing to move away from his agreement with Arafat to seek a role for the PLO in the negotiating process.

In addition, the sources said, Murphy wanted Hussein to clarify whether his insistence on negotiations taking place under "international auspices" means he wants an actual conference including the Soviet Union and other countries. Israel and the United States prefer a more informal arrangement that would have the other participating governments endorse the concept of direct talks between Israel and Jordan and then step aside.

However, the sources said, initial reports from Murphy indicated that Hussein was not ready to commit himself to a specific course on either of these sticking points.

Despite Redman's public insistence that the United States had not been looking for dramatic developments, the sources said Shultz had been hoping for more progress.