Prince Norodom Sihanouk said Monday he has resigned as head of the Cambodian resistance coalition, surprising the United States and other countries that hoped he would play a key role in Cambodian peace talks.

"For serious reasons that are, for the moment, impossible for me to enumerate and to explain, please allow me today to resign as president of Democratic Kampuchea (Cambodia)," Sihanouk said in a statement issued by his office here."I have decided to go into exile in France," he said, thanking Thailand and China, which have given him and his family refuge.

All through the previous week, Sihanouk had seemed about to take center stage in impending peace talks on Cambodia. Last week, he met in Bangkok with Secretary of State George P. Shultz, Japanese Foreign Minister Sosuke Uno and other Asian leaders attending a regional meeting.

Sihanouk, a former Cambodian head of state, had led a three-party guerrilla coalition fighting Vietnamese troops that invaded Cambodia in late 1978. The mercurial prince has previously quit as president, then changed his mind, making such shifts a part of his traditional diplomacy.

Vietnam has said it will withdraw all of its troops from Camobodia by 1990.

Shultz, speaking to reporters in Jakarta, Indonesia, said he didn't know how to interpret reports Sihanouk has resigned, adding that in recent meetings the prince seemed to take a "constructive" approach to the Cambodian problem.

"He has every intention of seeing this through," Shultz said of the Cambodian leader, who has in the past "resigned" from various positions only to re-accept them later.

In Tokyo, a Foreign Ministry official called Sihanouk's statement a surprise and said the ministry is trying to determine the prince's intentions.

"We hope Sihanouk continues in his role as a leader to the Cambodian problem," the Japanese official added, speaking on condition of anonymity.

A spokesman in Sihanouk's office said he wasn't sure if the prince would be carrying out his previous pledge to attend peace talks planned for July 25 in Indonesia.

Sihanouk was to leave Bangkok for France later today, the spokesman said.

In Jakarta, Indonesian Foreign Minister Ali Alatas said today that Sihanouk sent a letter to the Indonesian government apologizing for cancelling a visit that was to begin today, but saying without elaboration that he would go to Jakarta in late July.

Sihanouk also said he regretted he was cancelling visits to the countries of the Association of Southeast Asian Nations, or ASEAN, and to Japan.

The resistance coalition also includes the Communist Khmer Rouge, which brutalized Cambodia before the Vietnamese invasion, and the Khmer People's National Liberation Front led by former premier Son Sann.

Sihanouk said in his statement that his son, Prince Norodom Ranariddh, would represent him in the coalition.

The talks were to involve the three guerrilla factions, the Vietnamese-installed government in Cambodia, Vietnam, Laos and ASEAN members.

ASEAN foreign ministers and their Western allies declared during annual talks last week in Bangkok that Sihanouk should play a central role in the talks and a future Cambodian government.

They strongly endorsed Sihanouk's proposals that a coalition government comprising all the Cambodian factions be formed to supervise elections after a Vietnamese withdrawal and an international peacekeeping force be set up to prevent the Vietnamese or the Khmer Rouge from retaking power.