Japan's Prime Minister Yasuo Fukuda has failed to make a deal with the main opposition party to continue a naval mission backing forces in Afghanistan.
Fukuda (right) failed to win Ozawa round
Japan has been providing fuel for coalition forces in Afghanistan, but its mandate runs out on 1 November.
Mr Fukuda held talks with Democratic Party leader Ichiro Ozawa, who said he could only back such a mission if it was part of a United Nations operation.
There are fears the dispute could spark early elections in Japan.
The government has already lost control of the upper house of parliament at elections in July, and would not welcome a fresh poll for the lower house, correspondents say.
Mr Fukuda meanwhile is due to visit the United States next month, his first overseas trip since taking office.
Japan has refuelled coalition warships in the Indian Ocean since 2001 and the US and Japan both want an extension.
The prime minister sought the Democratic Party's backing for new legislation.
"I asked for his party's cooperation regarding the new anti-terrorism bill and explained the situation, but as of today we did not reach any agreement," Mr Fukuda said after he met the opposition leader.
Mr Ozawa said: "I told him that I cannot approve of it. We need to have principles, which means that unless it's part of UN operations, it would not be possible."
The two men are due to meet again at the end of the week.
The mission has been dogged by allegations that Japan supplied far more fuel to US forces than officially recorded - encouraging speculation that Tokyo might have helped supply the US war in Iraq, not just its operations in Afghanistan.
Japan's refuelling mission has proved controversial at home
Japan's constitution forbids it from fighting other nations but the government has recently tried to revise it to allow for a more robust defence policy.
In the past few years it has sent troops to Iraq on a humanitarian mission as well as supplying the coalition in Afghanistan.
The Iraq deployment ended in 2006, while the Afghan one appeared to come to an effective end on Monday, when a Pakistani destroyer took on a fresh load of fuel, Japanese media said.
The Associated Press quoted a Japanese defence official saying no further ships would be refuelled.