The son of Papua New Guinea's long-serving prime minister, Michael Somare, says his ailing father has decided to resign.

Arthur Somare told reporters Tuesday in the capital, Port Moresby, that his 75-year-old father has decided to step down in order to end a period of uncertainly about the country's political future.

Mr. Somare led Papua New Guinea to independence in 1975 and now is serving his third term as prime minister. But he took a leave of absence in December following charges of financial misconduct two decades ago, and has undergone heart surgery in Singapore three times since April.

Acting Prime Minister Sam Abal is expected to remain in office until new elections are arranged, likely next year.

Papua New Guinea is one of Asia's poorest countries, with a majority of its population living on subsistence incomes. However, a planned $15 billion liquid natural gas project headed by U.S.-based ExxonMobil is expected to bring increased prosperity.