US joins race to find stricken Indonesia submarine

The US military is sending airborne assistance to aid Indonesia's search for a missing submarine with 53 crew.

Indonesian authorities estimate they have just hours left to find the navy submarine before the oxygen runs out.

The KRI Nanggala 402 disappeared on Wednesday during exercises off the coast of Bali, sparking a frantic search to locate the stricken vessel.

An oil slick where it was thought to have submerged suggested damage to a fuel tank may have been a factor.

Pentagon spokesman John Kirby said the US was "deeply saddened" by the turn of events.

"Our thoughts are with the Indonesian sailors and their families," Mr Kirby said in a statement. "At the invitation of the Indonesian government, we are sending airborne assets to assist in the search for the missing submarine."