Nickel Asia, which accounts for about half of the Philippines' nickel ore output, expects to book windfall gains from the supply disruption that will keep nickel prices high, senior vice president and CFO Emmanuel Samson told Reuters.

The supply cut will be "huge", he said. "How do you cover that? The Philippines will have a difficult time covering that."

Indonesia and the Philippines are China's biggest suppliers of nickel ore, used in stainless steel and batteries.

Indonesia will effectively stop nickel ore exports from Jan. 1, 2020, Bambang Gatot Ariyono, the mining ministry's director general for coal and minerals, confirmed on Monday, as the country moves ahead with efforts to process more of its resources at home.

(Reporting by Enrico dela Cruz; editing by Richard Pullin)