NUKU'ALOFA, Tonga (AP) _ Tonga's octogenarian King Taufa'ahau Tupou has moved to end a power struggle by passing over his eldest son and handing the prime ministership to his youngest.

Prince Ulukalala Lavaka Ata was appointed to take over from outgoing Baron Vaea at a brief ceremony Monday.

Crown Prince Tupouto'a had been expected to take the post but has been locked in a dispute with his father about whether he would be allowed to choose his own Cabinet.

The king has refused to approve the dismissal from the Cabinet of members of the nobility he appointed for life.

Tonga, a South Pacific chain of some 150 islands 2,350 miles east of Australia, is a member of the British Commonwealth and has a government based on the British parliamentary model.

However, the constitution endows the king with ultimate political power. He appoints eight Cabinet ministers and two provincial governors to the 28-seat legislature. Nine seats are reserved for members of 33 noble families and nine are elected by the nation's 45,000 registered voters.