Israeli Prime Minister Shimon Peres warned today that time is growing short for progress toward Middle East peace, and appealed to Jordan's King Hussein not to "consign this moment to the fate of missed opportunity."

In an obvious reference to the swiftly approaching end of his term in office next October, when his right-wing coalition partner Yitzhak Shamir is due to take over, Peres described 1986 as "a crucial year."

"The atmosphere of peace is a very perishable commodity," he said. "Time will not stand still."

Building on what was viewed as a conciliatory speech to the United Nations last fall, Peres said that Israel is ready to enter talks with "a Jordanian or Jordanian-Palestinian delegation . . . without preconditions, . . . supported if necessary by an international forum."

"Our enemy is not the Palestinian people," Peres said. "Our enemy is terrorism."

Peres' remarks, in a speech to the Royal Institute of International Affairs at the start of an official five-day visit here, come at a time of rising hopes of new movement in the stalled peace process. His European swing coincides with a less publicized tour by the Reagan administration's Middle East troubleshooter, Assistant Secretary of State Richard W. Murphy.

Murphy and Peres met earlier this week in the Netherlands, and were to hold more private talks here late tonight. Last week, Hussein met here with Prime Minister Margaret Thatcher and Foreign Secretary Geoffrey Howe. All of the talks are believed to center on possibilities that there may be new negotiating room in the positions over which last year's efforts stumbled.

Those efforts, which followed President Reagan's 1982 call for a Jordanian-Palestinian federation, stemmed from a February agreement between Palestine Liberation Organization Chairman Yasser Arafat and Hussein. It called for an international conference in which Israel could negotiate with a joint Jordanian-Palestinian delegation over the Israeli-occupied West Bank and Gaza Strip.

Both the United States and Israel rejected the international context, and Israel insisted on direct, bilateral negotiations with Jordan. Also, both refused to talk to any Palestinian delegation that included representatives of the PLO.

The PLO refused to take the step that would help make at least U.S. acceptance possible -- clear recognition of Israel's right to exist and of U.N. resolutions supporting that right. Hussein insisted that an acceptable PLO-related delegation could be assembled, but efforts in that direction foundered.

Today, U.S., Israeli and British officials cautioned that they expect no "dramatic" new initiatives or immediate breakthrough. But all said that the parties most directly involved had made incremental movements in recent months, and were newly "motivated" to explore additional possibilities.

Hussein is said to be eager to demonstrate progress before March 1 -- when Congress is to reconsider a major U.S. arms package for Jordan that congressional disapproval forced the administration to withdraw last fall.

The United States, officials said, has gradually shifted away from a "procedural" to a "substantive" approach on peace talks. Encouraged by Peres' tentative willingness to accept an international conference for direct talks with Jordan, Murphy is exploring Israeli flexibility.

Last November's summit meeting between Reagan and Soviet leader Mikhail Gorbachev, some believe, has led to a lessening of tension between Moscow and Washington that could lead to acceptance of Soviet participation in the conference -- insisted on by Hussein but rejected last year by the Israelis.

Today, Peres said he was even willing to accept Syrian participation in the talks -- which Moscow wants but Arafat does not. "We have no objection to their coming," he said, but "if you ask my estimate, I don't believe Syria will negotiate."

Most importantly, in the view of U.S. and British officials, Peres' window of opportunity for peace progress is quickly narrowing.

Although he repeatedly has denied it in recent interviews, Peres is believed anxious to find a way to stay in office past the October deadline. To do so he would have to call new elections before then, on the basis of public support for policies a Shamir government is likely to try to reverse. His most promising path would be to push the peace process to a point where the Israeli public sees real possibilities for success under a continuing Peres government.

The United States and Western Europe also would like to see Peres find a way to stay in office. "The more days that go by," an official here said, "the greater the chance that the rotation will happen. But an election has to be over a real issue, and he has to be sure he can win."

All sides now are looking for areas of possible compromise. The United States reportedly would like a better understanding of how far Peres is willing to go toward organizing an international conference. Peres is said to be seeking answers from Western Europe and the United States on the extent to which they can persuade Hussein that the PLO is no longer workable for a joint delegation.