Prime Minister Shinzo Abe vowed again Friday to revise the Constitution, including amending war-renouncing Article 9 to allow Japan to exercise the right of collective self-defense.

At a meeting of a Liberal Democratic Party working group on the constitutional revisions, Abe emphasized that changing the Constitution has been a goal of the LDP since the party was founded 58 years ago.

"Now is the time for possible revision as we prepared the draft despite the general perception that it's almost impossible to amend the Constitution," Abe said at the working group's first meeting since the LDP returned to power in December.

Abe last week reconvened a study group of experts to mull four limited cases for exercising collective self-defense, renewing his effort to boost the Japan-U.S. alliance before his summit next week with President Barack Obama.

The four cases include Japan shooting down ballistic missiles aimed at the U.S. or providing logistic support to the U.S. military.

While Abe is trying to create momentum for the revision, Buddhist-backed LDP ally New Komeito remains hesitant.