Ahn Cheol-soo, the chief of a minor opposition party and a leading Seoul mayoral contender, on Wednesday accepted an independent rival's offer to compete in a preliminary race as a step to field a single candidate for the opposition bloc in the April 7 mayoral election.

The latest decision by Ahn, the chief of the People's Party, will pit him against former lawmaker Keum Tae-sup and other potential contenders in a preliminary election to pick a common opposition candidate outside the main opposition People Power Party (PPP).

Ahn announced his bid for the upcoming election in December, seeking to become the sole candidate for the entire opposition bloc. PPP, under which several powerful candidates are running, has been tepid, however, about Ahn's call to field a collective candidate for the opposition bloc.

"I propose not only candidate Keum but also all the other candidates in the broader opposition bloc (except for the PPP) that agree on regime change and punishing the Moon Jae-in administration come together to compete to pick a common candidate," Ahn said in a press conference.

As part of the proposal, Ahn said anyone who wins the preliminary election should be allowed to compete with a PPP candidate for the opposition bloc to be able to field a single common candidate for the mayoral election.

Ahn, a former software mogul, has been leading the latest opinion polls on favored Seoul mayoral candidates. The election is seen as a key barometer for next year's presidential election.

The Seoul mayor seat has been left vacant since the death of Park Won-soon in July. He was found dead on a mountain in Seoul in an apparent suicide after he was accused of sexually assaulting his former assistant. (Yonhap)