Ruling Democratic Party of Korea Chairman Jung Chung-rae formally declares his bid for the party leadership at the National Assembly in Yeouido, Seoul, Monday. Yonhap

Ruling Democratic Party of Korea (DPK) Chairman Jung Chung-rae formally declared his bid for the party leadership on Monday, pledging to stand by President Lee Jae Myung amid speculation about friction in their relationship.

The new leadership will be elected at the DPK's national convention on Aug. 17.

"As I have done so far, I will remain at the president’s side to the very end as part of a united team speaking with one voice alongside the party, the government and the presidential office," Jung said during a press conference at the National Assembly in Yeouido, Seoul.

Jung said he had spent the past year "holding high the banner of bold reform" as party chairman and pledged to become "an even stronger reform-minded leader" if reelected.