Polisario guerrillas said on Saturday they would soon send a high-ranking delegation to Morocco to meet King Hassan, in what appeared to be a major breakthrough in the 13-year Western Sahara conflict.

The Marxist-led Polisario Front, in a statement from its Algiers headquarters, gave no date or place for the meeting.In August, both sides accepted in principle a peace plan sponsored by the U.N. for the barren and remote former Spanish colony. Further progress foundered on King Hassan's refusal to hold direct talks with the Polisario.

But in an interview with the French magazine Le Point earlier this month, the Moroccan monarch indicated he had modified his position.

He said he would receive a Polisario delegation although he would not enter into negotiations over the territory. Until now, King Hassan has refused to accept the existence of the Polisario as anything but a group of Algerian-backed rebels.

"The doors of my palace are open. I am ready to hear everyone, to listen to their problems and know what they want for this part of the territory," he told the interviewer.

"They can come in their capacity as Polisario," he added.

The U.N. plan calls for a referendum offering independence or integration with Morocco. But many details remain to be settled, such as a formal ceasefire, an exchange of prisoners and the crucial question of who can vote.

The Polisario has been on the ropes since its main backer, Algeria, restored diplomatic ties with Morocco in May. After two leadership reshuffles it has adopted a more conciliatory tone.

The statement, carried by the official Algerian APS news agency, said:

"Knowing that the king of Morocco is a man of dialogue and considering that he has thus expressed his readiness . . . the (Polisario) executive committee has taken note of this constructive position which it considers a response to the Front's numerous appeals for dialogue," it said.

Moroccan officials were unavailable for comment, but diplomats in Rabat said they doubted the Polisario response was an attempt to embarrass King Hassan.

They said the Polisario needed to make a gesture after it shot down an American aid plane by mistake two weeks ago, killing five people.