KONTAN.CO.ID - JAKARTA. Indonesia's president ordered an all-out effort to find a missing submarine in a race against time to save the 53 crew, whose oxygen supply defence chiefs said would last only until Saturday.

Indonesia sent a helicopter and five ships to search waters north of the holiday island of Bali but found no signs of the KRI Nanggala-402, which went missing early on Wednesday during a torpedo drill.

"I have ordered the military chief, navy chief of staff, the search and rescue agency and other instances to deploy all the forces and the most optimal efforts to find and rescue the submarine crew," President Joko Widodo said on Thursday.

"The main priority is the safety of the 53 crew members."

Yudo Margono, the navy chief of staff, said the search was being aided by calm conditions but the crew's air supply would last only until Saturday.

Baca Juga: TIMELINE-The search for a missing submarine in Indonesian waters

"Hopefully before they can be found, the oxygen will be enough," he told a news conference in Bali.

The vessel had been cleared for use and was in good condition, he added.

The 1,395-tonne vessel was built in Germany in 1977, according to the defence ministry, and joined the Indonesian fleet in 1981. It underwent a two-year refit in South Korea that was completed in 2012.

Indonesia said several countries had responded to requests for assistance, with Malaysia and Singapore sending ships and Australia offering "help in any way we can".

The U.S. Defence Department is sending "airborne assets" to assist in the submarine search, Pentagon spokesman John Kirby said on Twitter.

U.S. Defence Secretary Lloyd Austin is scheduled to speak with Indonesian Defence Minister Prabowo Subianto on Friday "to convey our sorrow and to discuss how else the United States can be of assistance," Kirby said.

Editor: Yudho Winarto