Lawmakers will probably pass a bill by the end of the Diet session to set up national referendum procedures that would enable the Liberal Democratic Party to introduce amendments to the Constitution to expand the role of the Self-Defense Forces, according to a senior LDP official.

Yoichi Masuzoe, a member of the House of Councilors, told a gathering of foreign journalists and diplomats this week that the LDP hopes to reach agreement with the main opposition party, the Democratic Party of Japan, to pass the referendum bill before the end of June.

"The DPJ has already agreed in the Lower House," Masuzoe said. "The obstacle now is my (DPJ) colleagues in the Upper House."