Japan, the world's second-largest nickel user, called on Indonesia to remove restrictions on mineral-ore exports, saying it may complain to the World Trade Organization should compromise talks fail.

"The country's unilateral measures aren't appropriate," Takayuki Ueda, director-general of the manufacturing industries bureau of Japan's Trade Ministry, said yesterday in an interview in Tokyo. Japan, which would prefer to negotiate a solution, may file an objection with the WTO should Indonesia proceed with a complete ban on exports as planned in 2014, he said.

Indonesia said May 3 it would rein in exports of 14 minerals including nickel, copper, gold and iron ore from May 6. The curbs on those shipments, combined with a 20 percent tax on the remainder, are aimed at raising their value and boosting local smelting, potentially increasing costs for smelters in Japan, the third-largest economy. The resource-poor nation also suffered when China's restrictions on exports of rare earths sent prices soaring, and complained to the WTO this year.