Indonesia on Monday said it had made "urgent" requests for an explanation why the United States barred its military chief from travelling to the US. The US embassy in Jakarta on Monday apologised to the Indonesian government after its army chief was denied entry to the US.

General Gatot Nurmantyo was scheduled to attend a conference to be held on Monday and Tuesday in Washington, DC, upon an invitation from General Joseph Dunford, chairman of the US Joint Chiefs of Staff.

Foreign Minister Retno Marsudi said she had accepted an official apology from the deputy US ambassador in Jakarta, but still awaited a detailed explanation.

"We conveyed that we still await clarification, an explanation why this happened," Marsudi told reporters after meeting the U.S. envoy.

"There is a sense of urgency to this that we have conveyed to them," she said, adding that US officials were "trying to coordinate with relevant authorities in the US to find out what really happened".

Nurmantyo and his wife, who had obtained a visa from the US embassy in Jakarta, were supposed to depart on Saturday afternoon.

However, shortly before departure, there was a notice from the Emirates airline that Nurmantyo and his wife had been refused entry by the US Customs and Border Protection.

The US deputy ambassador to Indonesia, Erin Elizabeth McKee, said the US government regretted and apologised for the incident and hoped it will not happen again.

"We deeply regret the inconvenience that this incident caused and we apologise," McKee told reporters after meeting Foreign Minister Marsudi.

US Ambassador Joseph Donovan, who is not in Jakarta, also offered an apology to Marsudi, according to a statement on Sunday from the embassy.

McKee emphasised that the problem had been solved and Nurmantyo could travel to the US with no restrictions.

Nevertheless, McKee did not elaborate as to why Nurmantyo could not enter the US last weekend. "The US embassy is working hard to understand what is happening," McKee said.

However, Marsudi said Indonesia would continue asking the US government for an explanation for the rejection.