JAKARTA, Jan 3 (Reuters) - Shares of Indonesia"s leading coal miners fell on Monday after the government banned exports of coal for January due to concerns about low supplies triggering power cuts in the world"s biggest exporter of thermal coal. The decision is likely to send shockwaves through global markets since the Southeast Asian country exported around 400 million tonnes in 2020. Its biggest customers are China, India, Japan and South Korea. The government said on Saturday it brought in the ban because low coal supplies at domestic plants could lead to widespread blackouts, though said it planned to evaluate the decision on Wednesday. read more Shares of Indonesian miner Adaro Energy fell 3.1%, while Bukit Asam (PTBA.JK) lost 3.3% and Bumi Resources tumbled 2.9% in early trade. Indonesia has a so-called Domestic Market Obligation (DMO) policy whereby coal miners must supply 25% of annual production to state utility Perusahaan Listrik Negara (PLN) at a maximum price of $70 per tonne, well below current market prices. Ridwan Jamaludin, director-general of minerals and coal at the energy ministry, said at the weekend that the ban was temporary but if not imposed almost 20 power plants with 10,850 megawatts of power would have to shut. Ridwan said coal supplies to power plants each month were below the DMO, so by year end "there was a coal stockpile deficit". The Indonesian Coal Mining Association (ICMA) called on the government to revoke the ban, saying in a statement it was "taken hastily without being discussed with business players". The chairman of ICMA, Pandu Sjahrir, said the group met trade ministry officials at the weekend to try to reach a solution. "The main objective now is to avoid power outages. For the very short term, the solution is for ten of our biggest members to try to help with PLN"s shortage," he told Reuters on Monday. The association has said it was concerned about potential disputes with buyers if coal producers declared force majeure for not being able to deliver coal exports. South Korea, one of Indonesia"s main buyers, said while there were likely to be some delivery delays, the country expected 55% of January coal shipments that had been loaded to be delivered on time, its industry ministry said. "While the ministry expects Indonesia’s coal export ban would have limited short-term impact, considering the country’s coal inventory and coal shipments from other countries, including Australia, we need to closely monitor developments in Indonesia and other countries," the ministry said.