Former Japanese finance minister Yoshihiko Noda is expected to be named prime minister by the country's parliament Tuesday.

Emerging as the surprise winner in Monday's ballot to determine the chief of Japan's ruling Democratic Party, Noda will replace Naoto Kan, who resigned last week amid widespread criticism of his handling of the crisis caused by a massive earthquake and tsunami in March.

After his election, Noda made an immediate plea for unity in his divided party. Addressing party lawmakers from both chambers at a Tokyo hotel, he called on the Democrats to close ranks and stop bickering as they face tough challenges.

Noda stressed the importance of cooperation in addressing the nation's troubled economy, recovery from the March disasters, and ending the nuclear crisis from the damaged Fukushima power plant.

As an ally of the outgoing Kan, Noda is likely to continue many of his predecessor's policies. He is also considered a staunch supporter of the Japan-U.S. security alliance.

In Washington, a spokeswoman for the U.S. State Department, Victoria Nuland, said the United States is looking forward to continuing close cooperation with Japan and its next prime minister across a broad range of issues.

Noda will be Japan's sixth prime minister in five years. He will have to deal with a deeply divided parliament. While the ruling party has a solid majority in the lower house, the upper house is in the hands of the opposition Liberal Democratic Party and in a position to block any legislation.

Noda is expected seek a coalition with the opposition Liberal Democratic Party and a third party, but it is not clear whether the LDP will be willing to cooperate.

More than 20,000 people are dead or missing from March's earthquake and tsunami, and thousands more have been displaced from homes near the Fukushima plant.

Across Japan, homes and factories are operating on reduced power as the government conducts safety tests on all of the country's nuclear reactors.