The announcement Thursday that King Norodom Sihanouk of Cambodia would abdicate his throne because of poor health has raised new uncertainties for a country with a viciously divisive modern history and few symbols of national unity.

Though Sihanouk's intentions remained unclear, the declaration read aloud by his son, Prince Norodom Ranariddh, was the strongest indication yet that the mercurial 81-year-old monarch may finally be prepared to exit the political stage he has dominated for more than half a century.

Sihanouk had been scheduled to return Thursday from Beijing, where he has been receiving medical treatment for several months, but he delayed his trip.

In his letter, the king asked Cambodian officials to form a throne council to select his successor, who by law must have royal blood. Though Cambodian law provides for such a council to select a new monarch upon the death of a king, there is no provision for abdication.

Some analysts in Cambodia's capital, Phnom Penh, suggested that Sihanouk, alarmed by his failing health, may have announced his departure to prompt officials to make provisions for a successor. But Michael Hayes, publisher of the Phnom Penh Post, said: "We're having trouble figuring out exactly what it means. Everybody's confused about whether he's coming back, whether he's abdicated or not, whether he's sick or not."

Placed on the throne in 1941 by French colonial authorities who believed he was a malleable neophyte, Sihanouk instead became a patriotic hero, campaigning worldwide after World War II for an end to French rule and then announcing Cambodia's independence in 1953.

Soon after, he abdicated for the first time in favor of his father, freeing himself to enter politics fully and lead a national front government. But he was overthrown in a 1970 coup led by Lon Nol, a military commander backed by the United States during the Vietnam War.

In exile, Sihanouk formed an alliance with communist Cambodian rebels, whom he named the Khmer Rouge, and they took power in 1975. Sihanouk returned to his country, but his erstwhile allies kept him effectively under house arrest and killed more than a dozen of his relatives during a four-year reign of terror that claimed the lives of more than 1 million Cambodians. He went into exile again, returning to Cambodia in 1991 after Vietnam invaded and ousted the Khmer Rouge.

Sihanouk played a central role in negotiations leading to the withdrawal of the Vietnamese and the establishment of a new government under Prime Minister Hun Sen. Sihanouk, a rare source of authority for the riven country, was reinstated as a constitutional monarch in 1993.

But his political clout has long been on the wane. His efforts to broker an agreement among feuding parties after inconclusive national elections last year were rebuffed by political leaders and, in a huff, he left for China in January. Since then, he has threatened several times to abdicate.

"The king has been frustrated and unhappy for a number of months," Hayes said, adding that perhaps Sihanouk was floating the idea of abdication to measure the response of top officials.

Prince Ranariddh, who is president of the parliament, said he would seek permission to visit Beijing along with Hun Sen and the acting head of state, Chea Sim, in a bid to persuade Sihanouk to remain on the throne. Ranariddh, who has said he is not interested in becoming king, called his father's announcement "very regrettable and shocking for all Cambodians who love him and regard him as sacred."

Cambodia's King Norodom Sihanouk, 81, troubled by his failing health and waning influence, has threatened to abdicate several times this year.