A move by the ruling bloc to partially change the House of Representatives electoral system has been widely criticized as a political compromise by the Liberal Democratic Party to please coalition partner New Komeito.
The tentative agreement, reached Wednesday among the ruling parties, has met with strong protest both in and out of the alliance, leaving it unclear whether it will be finalized Tuesday as planned.
Prime Minister Junichiro Koizumi has told LDP Secretary General Taku Yamasaki to handle the matter with caution, even hinting that the plan should be revised to win opposition support.