As part of his administration's quest to revise the pacifist Constitution, Prime Minister Shinzo Abe said Sunday that he is willing to work on the issue with Osaka Ishin no Kai, an opposition party established by the city's former mayor, Toru Hashimoto.

Abe has been a strident proponent of revising the national defense policy defined by the charter's Article 9, which forbids Japan from using force to settle international disputes.

"It would be very difficult for the ruling parties alone to win two-thirds or more (of the Upper House). (But) there are parties that are favorable toward constitutional revisions such as Osaka Ishin no Kai," Abe said in an interview with NHK that was held Saturday and aired Sunday.