The legislation provides the legal basis for the largest foreign deployment for Japan's armed forces since World War II, which has angered some critics.

Opposition parties objected to the plan on the grounds that it would breach the Japanese constitution, which prohibits military forces from being used for purposes other than defense.

Opinion polls suggest that many Japanese people oppose the deployment of Japanese troops.

The BBC's Jonathan Head in Tokyo says the government also faces the difficult task now of defining exactly what the Japanese contingent will be allowed to do in Iraq.

Troops are supposed to stick to humanitarian work, and avoid conflict areas - but the prime minister himself has admitted such areas were hard to identify in today's Iraq.

Joining the coalition

A non-combatant reconnaissance mission is expected to leave by August, followed by a 1,000-strong contingent in October.

They will assist with resettling refugees, rebuilding and providing fresh water supplies.

The vote deteriorated into a wild shoving match at one stage of the committee meeting as outraged opposition legislators tried to push their way through to get at the committee chairman.

He cut short the debate to call a vote and, as the grappling spiralled out of control around him, pushed the bill through.

The vote marked a significant triumph for Prime Minister Junichiro Koizumi, who has long pressed Japan to deploy international peacekeeping troops in order to raise Japan's world profile.

At present, there are about 147,000 US troops in Iraq and 13,000 troops from other countries.

US General Richard Myers, the chairman of the Joint Chiefs of Staff, told US senators on Thursday 19 nations have sent troops to Iraq so far and 15 more have agreed to do so.