A search is continuing for a missing Malaysia Airlines passenger jet with 239 people on board.
The Boeing 777-200 disappeared from the screens of air-traffic controllers while flying over the South China Sea.
The plane was two hours into a flight from Kuala Lumpur to Beijing.
Vietnamese state media early on March 8 quoted a Vietnamese naval official as saying the plane had reportedly crashed off the Vietnamese coast.
Reports suggested Vietnamese planes had spotted what they believed were two oil slicks possibly caused by the downed airliner.
Malaysian Prime Minister Najib Razak told a news conference in Sepang, Selangor State, that "the U.S. Navy has agreed to send their vessels to be involved in the search operations that we've been conducting."
China has sent two ships to help search for the missing aircraft.
Malaysia Airlines said the plane's pilot was highly experienced, working at the airline since 1981.
Most of the 227 passengers are said to be Chinese, although there were travelers from 14 nationalities aboard.
Based on reporting by AP, dpa, and Reuters