U.S., Britain sending warships to help Philippine relief efforts

* U.S. aircraft carrier to arrive in 48-72 hours

* Toll expected to rise as rescuers reach devastated towns

* An estimated 10,000 killed in Tacloban city alone

* President declares state of national calamity

* Humanitarian groups describe desperate need for food (Adds details on U.S. and British military assistance)

By Andrew R.C. Marshall and Manuel Mogato

TACLOBAN, Philippines, Nov 12 (Reuters) - The United States is sending an aircraft carrier to the Philippines to help speed up relief efforts after a typhoon killed an estimated 10,000 people in one city alone, with fears the toll could rise sharply as rescuers reach devastated towns.

The USS George Washington aircraft carrier should arrive in 48 to 72 hours, the Pentagon said, confirming a Reuters report.

A statement said crew from the George Washington, which carries some 5,000 sailors and more than 80 aircraft, were being recalled early from shore leave in Hong Kong and the ship was expected to be under way in the coming hours. Other U.S. Navy ships would also head to the Philippines, it said.

The Philippines has been overwhelmed by the scale of Typhoon Haiyan, one of the strongest on record, which tore a path through islands in the central Philippines on Friday.

Rescue workers were trying to reach towns and villages on Tuesday that have been cut off, which could reveal the full extent of the loss of life and devastation from the disaster.

The arrival of the carrier and its aircraft will speed up the distribution of aid and ensure injured survivors can be evacuated to hospitals in unaffected parts of the country.

Britain is also sending a navy warship with equipment to make drinking water from seawater and a military transport aircraft, Prime Minister David Cameron said.

DEATH TOLL EXPECTED TO RISE

Officials in Tacloban, which bore the brunt of the storm, have said the death toll could be 10,000 in their city. There is grave concern for regions outside Tacloban.

"I think what worries us the most is that there are so many areas where we have no information from, and when we have this silence, it usually means the damage is even worse," said Joseph Curry of the U.S. organisation Catholic Relief Services.

The "sheer size of the emergency" in the wake of the typhoon was testing relief efforts, he told NBC's "Today" program on Monday, speaking from Manila.

John Ging, director of operations at the U.N. Office for the Coordination of Humanitarian Affairs, said "many places are strewn with dead bodies" that need to be buried quickly to prevent the outbreak of a public health disaster.