Japan pledged about 600 billion yen ($7.4 billion) in development aid and expertise after a summit Saturday with the leaders of the Mekong River region. Japan is seeking to strengthen its partnerships with Thailand - by far the biggest economy in the region and already a key Japanese manufacturing hub - Vietnam, Cambodia, Laos and Myanmar. This is the fourth summit since leaders from the six nations first met in 2009, according to a report of the Associated Press. Japanese Prime Minister Yoshihiko Noda emphasized continued cooperation with the region, saying, "The stability and development of East Asia is not possible without the stability and development of the Mekong region." "Japan will continue to vigorously promote cooperation with the Mekong region as a key area for assistance," he said at a joint press conference.