Debate over the security bills to overhaul Japan's postwar defense policies kicked off in the Upper House on Monday, with enactment of the unpopular proposals almost guaranteed even if all of the opposition parties band together to bloc its passage.

During a plenary session to begin deliberations on the bills, which would expand the scope of the Self-Defense Forces' missions overseas, the largest opposition Democratic Party of Japan said it will try to abolish the legislation.

Chances of blocking the two bills appear slim, however.