Prime Minister Yoshihiko Noda said Saturday that his government "cannot sidestep" a controversial tax hike that has turned into the leader's highest priority and largest potential stumbling block.

During a 30-minute group interview with 19 members of the international news media, Noda appealed for opposition cooperation on his tax plan, which would help the country pay for its escalating social security costs and ease global concerns about its massive debt.

"There is no waiting in responding to this question" of how to create a sustainable social security system, Noda said. "We're faced with an aging society and a declining birthrate unprecedented in the history of humankind and we cannot sidestep this challenge. I believe all the political parties fully understand this."