In an apparent about-face Tuesday, the Liberal Democratic Party agreed to vote in favor of the contentious tax hike and social security legislation in the Upper House on Wednesday.

But at the same time, the conservative party threatened to up the pressure on Prime Minister Yoshihiko Noda, president of the ruling Democratic Party of Japan, to get him to clearly promise to dissolve the Lower House for an election soon.

If Noda refuses to comply, the LDP might renege on its support for the bills and even attempt to submit a no-confidence motion against Noda in the Lower House, party sources said.