Nov. 7 (Bloomberg) -- Japan will join five Southeast Asian nations that share the Mekong River in a 10-year program to protect the region’s environment, as Prime Minister Yukio Hatoyama seeks closer ties with Asia.

Hatoyama and the leaders of Thailand, Vietnam, Cambodia, Laos and Myanmar agreed to establish a new partnership today at the inaugural Japan-Mekong summit in Tokyo, as Japan’s leader pledged 500 billion yen ($5.5 billion) in aid over the next three years. The Southeast Asian leaders thanked Hatoyama for the aid pledge and financial assistance for Mekong reforestation and water management.

Hatoyama is pushing for an “East Asian Community” modeled on the European Union, to eventually include a shared regional currency, as China increases investment and trade in the region.

“The Mekong region holds the key to my East Asian Community idea,” Hatoyama said in Tokyo following two days of meetings. “I’ve proposed a ‘Green Mekong’ plan to help the region’s effort such as water management to address climate change, and the proposal was adopted.”

Laotian Prime Minister Bouasone Bouphavanh expressed thanks for Japan’s pledge of aid and plan to invite 30,000 trainees to Japan over the next three years, and said more investment by Japanese firms in the Mekong region would be welcome.

Hatoyama announced in September plans to increase aid for developing nations to address global warming, and Japan’s new target to cut greenhouse gases by 25 percent by 2020.

Attendees included Thai Prime Minister Abhisit Vejjajiva and his Cambodian counterpart Hun Sen, whose countries have recalled their respective ambassadors after Cambodia named fugitive ex-Thai premier Thaksin Shinawatra an economic adviser.

Also present were Myanmar Prime Minister Thein Sein and Vietnamese Prime Minister Nguyen Tan Dung.

To contact the reporters on this story: Sachiko Sakamaki in Tokyo at Ssakamaki1@bloomberg.net;

Last Updated: November 6, 2009 22:46 EST