The leader of the main opposition People Power Party canceled part of his official schedule Tuesday, adding weight to speculation he could resign over disagreements with the party's presidential nominee Yoon Seok-youl.

The party informed reporters at short notice that Chairman Lee Jun-seok had canceled his attendance at a forum Tuesday morning, without providing a reason.

The notice added to speculation Lee could be considering resigning from at least one of his official titles, including co-chair of the PPP election committee and party chairman, after he appeared to have been sidelined in several decisions made by Yoon's campaign.

Among them was the campaign's recruitment of Lee Soo-jung, a professor of criminal psychology at Kyonggi University. The party chairman had publicly opposed her appointment, saying it would "run counter" to the direction in which the party has been going to prepare for the March 9 presidential election.

An aide to the chairman later explained that Lee did not want the professor on board because she is not liked by men in their 20s and 30s, who view her as a leading feminist, thus potentially affecting their votes.

Lee also expressed displeasure at not having been informed in advance of Yoon's visit to the central Chungcheong region this week.

"In that case, this is where it stops," he wrote in a terse post on Facebook late Monday night.

It was not immediately known whether Lee would attend his other scheduled events in the afternoon. (Yonhap)