Japan's ruling party has elected Finance Minister Yoshihiko Noda as its new leader, meaning the fiscal conservative will almost certainly become the nation's sixth prime minister in the last five years.

Noda defeated Trade and Industry Minister Banri Kaieda in a two-man runoff during voting Monday by Democratic Party of Japan legislators. Parliament is expected to elect him as prime minister Tuesday.

Former foreign minister Seiji Maehara, who was considered the most popular candidate with the public, ran third in the first-round balloting and was eliminated.

Outgoing Prime Minister Naoto Kan resigned Friday, fulfilling a promise he made earlier this year.

Mr. Kan's public approval rating had slumped amid widespread frustration with the government's handling of the disaster at the Fukushima Daichi nuclear power plant.

The new prime minister will face enormous challenges as Japan struggles to recover from the March 11 earthquake and tsunami and bring the nuclear power plant under control. More than 20,000 people are dead or missing from the twin disasters 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.

The new prime minister will also have to deal with a deeply divided parliament. While the DPJ 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.