With Japan's death toll at 686 people, the international relief effort has been spurred by the stark, globally televised videos of homes and offices rattled to near collapse and entire waterfront communities being washed away by a rising ocean.

The international community's assistance complemented the United States' expansive relief mission, which includes supplies, several warships, search-and-rescue teams, radiation-contamination specialists, and two officials from the U.S. Nuclear Regulatory Commission with expertise in boiling water nuclear reactors.

On March 13, the nuclear-powered aircraft carrier USS Ronald Reagan arrived off the coast of Honshu to support Japanese forces in disaster relief operations, the U.S. Department of Defense said in a statement.

In addressing one of the bigger potential threats, the international atomic agency's Incident and Emergency Centre has offered technical assistance to Japan in the wake of an explosion at the Fukushima Daiichi nuclear plant. An evacuation order for a 20-kilometer radius around the plant is affecting tens of thousands of people.

On March 12, the United Kingdom said it was sending a team of 59 fire service search-and-rescue specialists, two rescue dogs and a medical support team, according to the Foreign and Commonwealth Office.

With a scheduled arrival on March 13, the crew will immediately join the international search for survivors in shattered and inundated communities, the British office said.

The teams will take up to 11 tonnes of rescue equipment, including heavy lifting and cutting equipment to extract people trapped in debris, the government said.

The UK foreign office also dispatched a 10-member consular response team, including British Red Cross workers, to Japan on the morning of March 13, the government said.

The Republic of Korea (RoK) is sending two rescue dogs, two handlers and three assistants to carry out what are expected to be dramatic searches of people inside collapsed structures. The rescue teams were scheduled to arrive on March 12, Japan's Ministry of Foreign Affairs said in a written statement.

In China, Premier Wen Jiabao, who expressed "deep sympathy" to the Japanese government and people, made a formal offer of assistance. Members of the country's international rescue team were ready to depart for Japan if needed, Chen Jianmin, director of the China Earthquake Administration, told the government's Xinhua News Agency.

The United States is providing as many 11 warships, with their helicopters, to assist Japanese authorities in rescue and recovery missions.

The U.S. Agency for International Development was dispatching two urban search-and-rescue teams, one from Fairfax County, Virginia, and the second from Los Angeles County -- totaling 150 people and 12 canines trained to find survivors. They are scheduled to arrive Monday morning in Japan.

On March 12, the Japanese foreign ministry listed the 49 countries extending offers of relief, in no particular order: Australia, Taiwan, the United States, RoK, China, Mexico, Thailand, New Zealand, Israel, Singapore, Indonesia, Azerbaijan, India, Russia, Turkey, Germany, France, Belgium, Ukraine, Slovakia, United Arab Emirates, Switzerland, Hungary, Poland, Jordan, the United Kingdom, Chile, Spain, Greece, Hong Kong, Pakistan, Denmark, Serbia, Uruguay, Mongolia, Ecuador, Iran, Kyrgyz Republic, Malaysia, Argentine, Philippines, Canada, Italy, Sweden, Kosovo, Iceland, Norway, Romania, and Slovenia.