March 11 (Reuters)- Countries and aid groups are offering to help Japan's rescue efforts after a powerful earthquake rocked the country, triggering a 10-metre tsunami that swept away everything in its path, including houses, ships, cars and farm buildings on fire.

Following are a list of aid offers.

* U.S. President Barack Obama said the United States stood "ready to help the Japanese people in this time of great trial". The U.S. military in Japan has opened its airfields to commercial aircraft the disruption of operations at Japanese airports, CNN quoted the Pentagon as saying.

* The United Nations said 30 international search and rescue teams were on alert to go to Japan to provide assistance.

* South Korea is initially sending 40 emergency rescue officials who are on standby to fly in by government plane when they get clearance, its foreign ministry said.

* Chinese earthquake rescuers are "fully prepared" to go to Japan to join earthquake relief work if needed, state media quoted the country's top seismological official Chen Jianmin as saying.

* Thailand will offer 5 million baht ($165,00) aid to Japan and will consider giving more when the extent of the damage is known, Thai Foreign Ministry spokesman Thani Thongpakdi said.

* British Foreign Secretary William Hague said Britain was in contact with the Japanese government and he has asked the country's ambassador in Tokyo to offer all assistance. ($1=30.37 Baht) (Reporting by Reuters bureaux, compiled by Asia Desk)