TOKYO, JUNE 5 -- Leaders of two of Cambodia's warring factions signed an agreement today calling for a conditional cease-fire but the powerful Khmer Rouge refused to back the initiative, giving it little chance of success.

Prime Minister Hun Sen of the Vietnam-backed Cambodian government and Prince Norodom Sihanouk, nominal head of a three-party guerrilla coalition, signed the document aimed at ending 11 years of civil war.

But the Khmer Rouge, which boycotted the talks after it was included in Sihanouk's coalition rather than being given separate status, refused to sign and said it would not follow the agreement.

Until now in a process that began two years ago, peace talks have included all four warring groups -- the Hun Sen government and the three guerrilla groups as separate entities. But Japan, which sponsored the talks, reportedly gave in to Hun Sen's demands that the Khmer Rouge be placed in Sihanouk's coalition.

The proposed armistice would take effect on the first day of the formation of a national council, which the two signers of the agreement said would take place by late July.

The United Nations-proposed council would represent Cambodian unity while internationally supervised elections are held and would be composed of six representatives of each side.

"I have agreed to a cease-fire and Son Sonn's army is also willing to stop fighting," said Sihanouk. Son Sonn heads the other non-Communist faction in the coalition. "But the Khmer Rouge are not obliged to follow the communique," Sihanouk said.

Khmer Rouge leader Khieu Samphan attended the two-day meeting in Tokyo that produced the document, but walked out after he was not given the status he sought.

Japan then gave in to pressure by Hun Sen to hold two-way talks, sidelining the Khmer Rouge, the guerrilla group held responsible for the deaths of over a million Cambodians during four years of rule that ended with their expulsion by the Vietnamese in 1979.

The two signers of the Tokyo communique called for reconvening "as soon as possible" the Paris-based International Conference on Cambodia, which collapsed last August.

Khieu Samphan, in a statement issued after the communique, said the Khmer Rouge would not observe the agreement. "We . . . cannot be held responsible for the implementation of any agreement which {we have} not signed," he said.

Khieu Samphan said his camp opposed the wording of the communique, which said all participants in Tokyo were "seeking a comprehensive political solution."