Tokyo Gov. Yuriko Koike said Tuesday she will step down as president of Kibo no To (Party of Hope) — the opposition force she founded — in a surprise move likely to deal a fresh blow to a struggling party facing tepid support.

Koike's decision to resign as Kibo no To president came less than a week after the party attempted a fresh start by electing young lawmaker Yuichiro Tamaki as a co-leader to serve alongside the populist governor. Tamaki holds the same conservative position as Koike on revising the pacifist Constitution and beefing up the nation's national security.

"I founded this party, but based on the assumption that you will continue to follow this party's basic direction we've already set forth, I'd like to resign as party president," Koike told a gathering of rank-and-file members of Kibo no To in Tokyo. "I will continue to support you where appropriate," she added.