Japan's refuelling mission has proved controversial at home
Japan's lower house of parliament has voted to extend a controversial mission backing US operations in Afghanistan.
Prime Minister Taro Aso had campaigned to keep the mission going, saying Japan should contribute to global security.
But many opposition members are against the proposal, saying it breaches the country's pacifist constitution.
The bill is likely to be rejected in the opposition-controlled upper house, before the more powerful lower house passes it into law.
Japan's constitution forbids it from fighting other nations, but in recent years the government has tried to revise the rules to allow for a more robust defence policy.
But the issue is an emotive one, and many MPs have argued that Japan should not be involved in military operations at all, however tangentially.
Japan has refuelled coalition warships in the Indian Ocean for several years, but the mission was temporarily halted last November because the opposition-dominated upper house refused to vote on the issue.
This time round, though, it has other priorities in mind.
Correspondents say that the main opposition Democratic Party of Japan (DPJ) hopes that by letting the bill pass, there is now no excuse for Mr Aso to postpone calling a snap general election.
Mr Aso's Liberal Democratic Party (LDP) has dominated Japanese politics for more than 50 years, but polls show the DPJ is now in a strong position to gain seats if an election is called soon.