Opposition parties prepared Wednesday to pass a resolution ousting a senior Liberal Democratic Party lawmaker as head of an Upper House committee, setting the stage for a showdown with the ruling bloc before the Upper House election in July.

If passed, it would mark the first time a committee chair has been dismissed. The LDP lacks an overriding two-thirds majority in the chamber.

The seven opposition parties, including the Democratic Party of Japan, Your Party and Nippon Ishin no Kai (Japan Restoration Party), submitted the resolution Tuesday to sack Yoriko Kawaguchi of the LDP as the head of the Upper House Environment Committee for failing to get permission from the Diet to extend a trip to China by one day. Her absence forced the committee to cancel a session scheduled for April 25.

Committee heads in both chambers are required to get approval for such leaves.

Kawaguchi said the two-day trip in late April was extended to accommodate a last-minute meeting with China’s State Councilor Yang Jiechi.

On Wednesday, the LDP and its junior coalition partner, New Komeito, boycotted the Upper House Budget Committee session on the fiscal 2013 budget in defense of Kawaguchi and to protest the action taken by the opposition camp. This is the first time in decades that a ruling bloc has refused to deliberate on a bill it sponsored.

After hours of intermittent negotiations between the LDP and the DPJ’s Diet affairs leaders, both sides agreed to vote on the resolution Thursday to prevent delay of the passage of the 2013 budget, whose vote is slated for next Wednesday.

The former foreign minister is refusing to resign, claiming the meeting with Yang served Japan’s national interest amid intensifying tensions with Beijing over the sovereignty of the Senkaku Islands.

“I will not resign. . . . I will leave the decision to the party,” Kawaguchi said Wednesday.