The United States is sending an undersea Navy drone capable of exploring waters nearly 15,000 feet deep to potentially help search for any sunken wreckage of Malaysia Airlines Flight MH370, the Pentagon said on Monday.

The US disclosure that it was pre-positioning the sonar-equipped Bluefin "autonomous underwater vehicle" in Australia came hours after Malaysia announced that the jetliner which disappeared over two weeks ago had crashed in the southern Indian Ocean.

All 239 people on board were presumed dead, airline officials said.

"We have more than 200 families out there that are grieving right now. They just got some stark news today from the Malaysian government," said Pentagon spokesman Rear Admiral John Kirby, adding the "the whole world grieves with them."

The Bluefin drone is just over five meters long and weighs 800kg, according to a Navy factsheet. Kirby said it can operate for more than a day at slower speeds.

The decision to pre-position the equipment in Australia comes in addition to the previously announced deployment of a "Towed Pinger Locater," essentially a high tech piece of sonar

equipment which can detect an aircraft's black box.

Time is critical, since the locator beacons on black boxes - the cockpit voice recorder and flight data recorder - fade out after about 30 days.

The US military loaned this locator technology to France during its effort to locate the black box from an Air France jetliner that crashed into the Atlantic Ocean in June 2009.

If it is used in the search for the Malaysian jetliner, it is expected be towed behind an Australian commercial ship.

Expected to be in Perth tomorrow

Both the undersea Navy drone and the towed pinger locator were flown out of a New York airport on Monday and were expected to arrive in Perth, Australia on Tuesday, the Pentagon said.

Ten American civilian personnel and uniformed members of the military were also flying to Australia to operate or prepare the equipment, it said.

But in both cases, the Pentagon cautioned that the US technology would only be employed once the search area was significantly narrowed.

"In order for this technology to be useful, you have to have an identified area on the sea bottom that you want to go take a look at," Kirby said.

"You have to be able to go give it some parameters - and right now we're just not there."

- Reuters