Egyptian President Hosni Mubarak indicated today he did not believe efforts by King Hussein and the Palestine Liberation Organization to reach an agreement on new American-sponsored peace negotiations had reached a dead end. He urged the two to resume their talks.

Speaking at an airport press conference in Islamabad, Pakistan, where he was winding up a 12-day Asian tour, the Egyptian leader said it was "imperative for our Palestinian friends to join Jordan in order to facilitate the negotiations to resolve the problem."

Reports of a break between PLO chief Yasser Arafat and the Jordanian monarch, over acceptance of President Reagan's plan as a basis of negotiations, "may not be quite precise," news agency reports reported him as saying. "We believe there is still a glimmer of hope."

Mubarak's comments came after receiving a telephone call this morning from Reagan and appeared aimed at keeping hopes alive for a reconciliation of the PLO and Hussein, who announced Sunday he was giving up his efforts to negotiate a compromise.

Upon arriving here, Mubarak said Reagan had reaffirmed his intention of pursuing his peace initiative and still hoped Arafat and Hussein would reach an agreement on entering peace talks.

Mubarak gave no indication of what he thought the Reagan administration would do next after the PLO rejected last weekend a proposed joint resolution with the king approving negotiations on the basis of Reagan's plan.

The breakdown in PLO-Jordanian negotiations represents a setback for Egyptian policy as well as that of the Reagan administration. It seems certain to complicate Mubarak's diplomacy, aimed at getting other Arab states to restore their relations with Cairo.

Egyptian policy makers indicated peace talks involving Jordan, Israel and the Palestinians could serve to justify Egypt's peace negotiations and treaty with Israel and help convince most of the 19 Arab states that broke ties with Egypt in 1979 to reverse their decision.

Mubarak repeated his argument with the PLO leadership that "the time element is not in favor of a solution" to the Middle East problem and that a lack of progress toward negotiations before the onset of the U.S. presidential election campaign would only play into Israeli hands.

"In this situation, we may make it easy for the Israelis to augment their efforts to build more settlements and practically to cover the West Bank and Gaza Strip with new settlements in such a way that would make it most difficult--tantamount to impossible--to eradicate them," he said.