美国派遣航母援助菲律宾的救灾工作
A US aircraft carrier and its escort of two cruisers are due to arrive off the Philippines to help communities devastated by Typhoon Haiyan.
美国一艘航空母舰与两艘护航舰将抵达菲律宾，救助被台风海燕破坏的地区。
The USS George Washington will expand search-and-rescue operations and provide a platform for helicopters to move supplies, the White House said.
The top US commander in the Philippines told the BBC that US military support would be on an unprecedented scale.
Some 11 million people have been affected by the typhoon.
Although the official death toll stands at more than 2,300, local officials and aid workers fear it could rise much higher.
With images of the suffering flashed around the world, a huge international aid effort has swung into operation.
The USS George Washington is expected to arrive off the Philippines later on Thursday along with its escort ships, the US Navy said. Two US destroyers have already arrived in the Philippines and other US vessels are expected to arrive in about a week, it added.
On Wednesday the US also ordered the activation of a hospital ship, the USNS Mercy. However, if deployed it would not reach the Philippines until December.
Marine Brigadier General Paul Kennedy, commanding general of the 3rd Marine Expeditionary Brigade in Japan, told the BBC that the US aid effort was being stepped up to a level that has "probably never been applied" to a humanitarian crisis.
He said the arrival of the USS George Washington would triple the number of available helicopters. As well as search and rescue capabilities, the helicopters can deliver hundreds of thousands of gallons of water every day, he added.
Other countries have also pledged help in the shape of financial aid, relief supplies or emergency teams.
Britain is sending a team of medical experts, a Royal Navy warship and an RAF transport aircraft.
Japan is also preparing to send up to 1,000 troops as well as naval vessels and aircraft, Defence Minister Itsunori Onodera said.
Orla Fagan, at the UN's Humanitarian Affairs office in Manila, said that after a slow start, the aid effort was now accelerating.
"People are angry, they are distressed, they are traumatised, and we are trying to get this stuff out to them," she said.