Japan's leading opposition Democratic Party has chosen 61-year-old Harvard-trained former Deputy Prime Minister Katsuya Okada as its top leader.

Okada won in a runoff vote Sunday against Goshi Hosono after another contender, former Health Minister Akira Nagatsuma, was eliminated in the first round. He faces the daunting challenge of uniting and rebuilding public trust in the Democratic Party, which has yet to recover from its electoral defeat by the Liberal Democrats in late 2012.

The Liberal Democrats further secured their dominance of Japanese politics in a snap election last month called by Prime Minister Shinzo Abe to seek support for his economic policies and conservative political agenda.

After his win, Okada vowed to restore his party's prestige, saying Japan needs a viable opposition to counter the Liberal Democrats.