The United States should remember the Vietnam War's painful lesson on the limits of power as it considers arming a non-communist Cambodia led by Prince Norodom Sihanouk.

Vietnamese forces are finally leaving that war-ravaged nation, a decade after driving the genocidal Khmer Rouge from power, but the threat of renewed civil war remains.After talks last week in Jakarta, it appears possible the government of Prime Minister Hun Sen, installed and to be left in Phnom Penh by the departing Vietnamese, may share power with the 67-year-old prince.

Sihanouk would return home this fall and again become head of state. But Hun Sen opposes Sihanouk's insistence that the Khmer Rouge must be given some representation in the new government.

Meantime, the United States is considering providing military aid to Sihanouk to bolster the non-communist resistance during the jockeying for power as the Vietnamese depart.

For good reason, the adjective "mercurial" of-ten precedes Sihanouk's name.

American diplomats should be wary when the wily prince hints he might embrace Hun Sen and forsake the Khmer Rouge, the maniacs who in the 1970s murdered more than 1 million Cambodians.

An accommodation between Hun Sen, supported by Moscow, and Beijing-backed Sihanouk would seem to be a long shot.

But those betting on such an alliance note that the Soviet Union and China are planning to hold their first summit in three decades.

No one knows whether Beijing will continue to bankroll the 35,000 armed and dangerous Khmer Rouge guerrillas who have the support of about 10 percent of the populace.

If Washington plays a role in Cambodia's future, it should not be as an arms supplier.

To some older Cambodians, Sihanouk is a symbol of better times, but he has no military power.

The United States should not supply arms to any faction in Cambodia, certainly not to a group incapable of challenging the dreaded Khmer Rouge on the battlefield.