Australia, Malaysia and Singapore have already joined the Indonesia-led search which comprises 15 ships and 30 aircraft, as anguished relatives of the 162 passengers awaited news of their loved ones.

Search teams are expected to focus on the area around Belitung Island, near West Kalimantan this morning, where a patch of oil has been spotted.

US State Department spokesman Jeffrey Rathke confirmed Jakarta had asked the US to assist the search, saying it would take “a little bit of time” to evaluate the request.

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“We are reviewing that request to find out how best we can meet Indonesia’s request for assistance,” he said.

Pentagon spokesman Rear Admiral John Kirby said the aid could include “some air, surface and sub-surface detection capabilities”.

“We stand ready to assist in any way possible,” he added.

In a statement on its website, China’s Defence Ministry said it had sent a warship to the South China Sea and planes “have begun preparatory work” for search operations.

Indonesian transport minister Ignasius Jonan said the search was focused on a 129-square-kilometre area of the Java Sea between Belitung Island, off Sumatra, and Borneo island.

He said the sea there was only 50 to 100 metres deep, which would be a help in finding the plane. Ships could hunt around the clock, but aircraft were expected to suspend operations at dusk.

Air force spokesman Hadi Tjahjanto said searchers were checking a report of an oil slick off Belitung.

“We are making sure whether it was avtur [aviation fuel] from the AirAsia plane or from a vessel because that location is a shipping line,” he said.