Indonesia has asked the United States for help to find the AirAsia jet that went missing on Sunday carrying 162 people, according to the US State Department.
"Today we received a request for assistance locating the plane, and we are reviewing that request to find out how best we can meet Indonesia's request for assistance," State Department spokesman Jeff Rathke told a news briefing.
Mr Rathke said the Indonesian request was made via a diplomatic note to the US embassy in Jakarta. He declined to give details of the request.
"Our embassy, of course, is focused on finding... ways to be responsive. Of course, we've been in close contact with Indonesian officials since the disappearance of the plane," Mr Rathke added.
The Indonesia AirAsia plane, an Airbus A320-200,disappeared after its pilot failed to get permission to fly higher to avoid bad weather during a flight from the Indonesian city of Surabaya to Singapore on Sunday.
The head of Indonesia's search and rescue agency has said the missing jet could be at the bottom of the sea after it was presumed to have crashed off the Indonesian coast.
However, there is "insufficient evidence" that objects spotted in the sea by Australian planes in an where the plane is believed to have gone down are from the missing AirAsia plane.
When the question of possible wreckage was raised at a press conference earlier today, Indonesian vice president Jusuf Kalla said there was "insufficient evidence" so far and ships in the area were being asked to investigate.
He confirmed there was no distress signal sent by the flight QZ8501 and communications were normal until cut off.
Earlier, a rescue official said the aircraft was likely to be at the bottom of the sea.
The flight crew of the plane had asked to divert due to safety fears amid stormy conditions before contact was lost with air traffic control. It was on its way from Surabaya in Indonesia to Singapore.
Henry Bambang Soelistyo, of the national search and rescue agency, said: "Based on the co-ordinates that we know, the evaluation would be that any estimated crash position is in the sea, and that the hypothesis is the plane is at the bottom of the sea."
The search for the missing plane, which had 155 passengers and seven crew on board, resumed this morning, after being suspended due to poor weather conditions.
12 navy ships, five planes, three helicopters and a number of warships are searching an area of east and southeast Belitung island and nearby waters, said First Admiral Sigit Setiayana, of the Naval Aviation Centre Commander at the Surabaya air force base.
He said visibility for the search is good. "God willing, we can find it soon," he added.
AirAsia Chief Executive Tony Fernandes spoke yesterday of his sadness and thanked people for their support. "This is my worst nightmare," he said.
"My only thoughts are with the passengers and my crew. We put our hope in the SAR (search and rescue) operation and thank the Indonesia, Singapore and Malaysian governments."
He said he was "touched by the massive show of support", especially from fellow airlines.
Mr Fernandes said his heart "bleeds" as the families of those missing await news.
Writing on Twitter, he said: "Keeping positive and staying strong. My heart bleeds for all the relatives of my crew and our passangers (sic)."
Keeping positive and staying strong. My heart bleeds for all the relatives of my crew and our passangers. Nothing is more important to us.— Tony Fernandes (@tonyfernandes) December 29, 2014
The airline boss said he had travelled to the Indonesian capital, Jakarta, to liaise with those in charge of the search and rescue mission, but planned to go back to Surabaya where families of those on board the plane are desperately awaiting an update on the situation.
Some relatives are based in Singapore, where they would have hoped to meet their family members safely off the plane yesterday.
The airline said it is providing whatever support it can to all those affected.
It said: "AirAsia Indonesia's primary focus remains on the families and Sunu Widyatmoko, chief executive officer of AirAsia Indonesia, is currently stationed at the family centre in Surabaya.
"We have been keeping the families updated on the search and rescue efforts as well as provide emotional support. Another group of AirAsia officials are providing the same to the families based in Singapore."