Japanese Prime Minister Yoshihiko Noda has dissolved the lower house of parliament, setting up a general election expected to bring a defeat to his ruling Democratic Party of Japan.

Mr. Noda's move to dissolve the lower, more powerful legislative body came after the opposition Liberal Democratic Party agreed to a series of key reforms, including deficit-shrinking and electoral reform measures.

Ex-prime minister and current LDP chief Shinzo Abe would return to lead the government if the opposition party wins the lower house, as polls suggest. But observers say a weak coalition is almost certain to emerge from the polls, which are to be set for December 16.

It will be the first general election since 2009, when the DPJ upset the LDP, which had ruled Japan for most of the post-World War Two era. Mr. Noda's DPJ has suffered low approval ratings, in part because of an unpopular tax increase and a series of scandals.

Japan's new leaders will be faced with what to do about deep-rooted problems in its stagnant economy, which has been riddled by a massive public debt, rapidly aging population and recovery from last year's massive earthquake and tsunami.

They will also have to deal with a simmering dispute with China over a series of uninhabited islands in the East China Sea. Tokyo purchased the islands from their private landowners earlier this year, prompting angry protests in Beijing.

Ex-prime minister Abe, an outspoken nationalist, has taken a strong stand against China, leading many to fear that the important relationship between the two Asian giants would further deteriorate if he were to retake the position.