Government officials have said the ban is aimed at increasing value-added industries in Indonesia’s economy by requiring miners to build smelters in the country, but the policy has been roundly criticized by both foreign and domestic companies as short-sighted and nationalistic. Some say it is driven by political motives ahead of legislative and presidential elections this year.

Industry experts noted that the export ban had been in the works since a mining law was passed in 2009, but that Mr. Yudhoyono’s government, apparently realizing the potential impact that it could have on jobs, taxes and royalties, had only created uncertainty and confusion by granting a reprieve until 2017.

“The most significant metal producers shouldn’t expect any negative impact," said Bill Sullivan, a lawyer and mining industry adviser in Jakarta. "The real story is how the government could have left it to the night before to come to grips with this. It’s been an appalling failure of government policy making.”

Mr. Sullivan said that midsize nickel and bauxite miners could be unfairly hurt the most by the new regulation if companies hired to build smelting facilities failed to do so by 2017.

“Why should they be penalized if the third party they were relying on hasn’t built the smelter?” he said.

Marwan Batubara, director of Indonesian Resources Studies, a nongovernmental organization in Jakarta specializing in public policy, accused the Indonesian government of “surrendering” to pressure from large international mining companies in allowing ore exports to continue as usual until 2017.

Because of that, he said he did not expect any noticeable impact in global supply of minerals from Indonesia like nickel and bauxite. China, for example, is a major importer of Indonesian nickel.