New Komeito, a member of the three-way ruling bloc, appears to be unhappy at the prospect of seeing the New Conservative Party, the smallest coalition member, swallowed up on Monday by the biggest, the Liberal Democratic Party.
Analysts say New Komeito fears it may have to abandon its comfortable position within the alliance and that its ties with the lay Buddhist group Soka Gakkai could face greater scrutiny.
New Komeito leader Takenori Kanzaki has said, "To be honest, a three-party alliance is desirable for us." Meanwhile, Chikara Sakaguchi, a New Komeito lawmaker who serves as health minister, said it is "regrettable" to see such a merger.