Japan's upper house is set to hold its final vote on bills to expand the role of the country's military abroad.
The measures are expected to pass, despite public protests, as Prime Minister Shinzo Abe's ruling coalition controls the House of Councillors.
The controversial changes will allow Japanese troops to fight overseas for the first time since World War Two.
The vote is going ahead despite last-ditch attempts to delay it by opposition politicians on Thursday.
Opposition parties have promised to keep trying to delay the bills' passage, through censure motions and other tactics, possibly including walking at an extremely slow pace to the final vote.
What is collective self-defence?Japan's post-World War Two constitution bars it from using force to resolve conflicts except in cases of self-defence.
Mr Abe's government has pushed for security legislation that would allow Japan's military to mobilise overseas when these three conditions are met:
The bills have prompted large public protests for months.
Critics say that the changes, which re-interpret rather than formally change the constitution, violate Japan's post-war pacifism and could lead it into unnecessary US-led wars abroad.
Supporters of the measures, which are backed by Washington, insist they are essential for the defence of Japan and its regional allies, and will permit greater involvement in peacekeeping activities around the world.
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