Lack of clarity on new Indonesian regulations on thermal coal exports has added to loading delays, sources said Thursday.

Indonesian customs authorities now require coal exporters to possess what is called an IUP OPK certification, which is a license for the transportation and trading of coal, a source close to the energy ministry said.

Coal buyers in the Philippines and South Korea said suppliers in Indonesia had notified them that they were unable to ship out cargoes as they were waiting for customs authorities to certify that they were in compliance with the new regulation.

Several Indonesian coal shippers have already had to cope with loading difficulties due to heavy rains in both eastern and southern Kalimantan.

A thermal coal buyer in Japan said, however, that he had not been notified of any delays in shipments by coal producers in Indonesia.

A Philippine buyer said his suppliers are having difficulty securing the customs certification that will allow them to ship out coal, while a South Korean market source said a trading company experienced a three-week delay in the loading of Kalimantan coal for delivery to a customer in the North Asian country.

"There is no problem with the regulation which was issued by the ministry in mid-2013," an Indonesian trader said. "The customs authorities just have to be briefed about the export license regulation which is one of the rules required to implement the 2009 Indonesian coal and minerals mining law."

Customs authorities are requiring all exporters to produce an IUP OPK certification even though Indonesian coal producers holding coal contracts of work prior to the passage of the 2009 law already possess an IUP OPK even after their contracts were converted into mining licenses, the source said.

New miners granted licenses after the mining law was passed are required to produce such certification, he said.

"Hopefully, the [energy ministry] will soon be able to clarify the issues and mechanics of the new export licensing regulation to the customs officials," he added.

All new mining license holders who have completed exploration and are in the operational stage of developing their mines, are qualified to apply for an IUP OPK, he pointed out. Trading companies that export coal, can use the IUP OPK possessed by their Indonesian coal suppliers, he added.

Energy ministry officials were not available to comment on the issue.