Kenji Eda, president of minor opposition party Yui no To, met Friday with Nippon Ishin no Kai (Japan Restoration Party) co-leader Shintaro Ishihara to explore ways for a possible merger but was told such talks should not be held until June 22, when the Diet closes, participants in the meeting said.

Takeo Hiranuma, a Nippon Ishin executive, emphasized that Eda only "paid a courtesy visit" to Ishihara, and that the two leaders did not go into any details of their parties' apparent policy differences.

"Ishihara told (Eda) that there won't be such talks until June 22," Hiranuma told reporters after the meeting at Nippon Ishin's head office in Tokyo's Akasaka district.

Former Tokyo Gov. Ishihara, a hawk calling for revision of the pacifist Constitution, has remained reluctant to join forces with Yui no To, given its stance to defend the Constitution.

Meanwhile Nippon Ishin and Yui no To have already decided to form a joint parliamentary group in the Upper House, and many Nippon Ishin members are willing to merge with it.

Ishihara's reluctance thus result in no merger talks being held, or he and his allies being isolated in their own party.

Osaka Mayor Toru Hashimoto, the other co-leader of Nippon Ishin, has pushed for the merger. On Monday, he even signaled that someone other than himself should lead the new party if it goes through.

Nippon Ishin is believed to be split between the Osaka-based members loyal to Hashimoto, and more right-leaning members in Tokyo led by Ishihara.

Yui no To is a minor party consisting of 15 Diet members who bolted from Your Party.