TOKYO, SEPT. 5 -- Japan's sputtering effort to aid the multinational military force in the Persian Gulf remained stalled today as union seamen refused to sail out of Japan with a cargo of vehicles urgently requested by U.S. forces in Saudi Arabia.

The freighter Sea Venus, illuminated by the lights of TV news teams, swung at anchor in Nagoya Harbor tonight as government officials struggled to persuade the ship's owners and crew to set off for Saudi Arabia with their shipload of 800 four-wheel-drive trucks and vans. Leaders of the Seamen's Union and officials of the shipping line Kanbara Marine were balking on grounds that ship and crew might run into danger in the gulf region.

Meanwhile, Japanese media reported a dispute over who will pay the bill for a Japan Air Lines charter flight that brought 70 Japanese hostages home from Iraq earlier this week. And the government said it has so far lined up a total of three doctors for the medical team that Prime Minister Toshiki Kaifu promised he would dispatch to the gulf region; two weeks ago, Kaifu had talked about a medical unit of more than 100 doctors and nurses.

All these problems illustrate the confusion and controversy surrounding Japan's first major effort since World War II to take an active role in a foreign crisis.

As an economic superpower with trade relations all over the globe, Japan has been moving toward a more active role in world affairs. Kaifu noted on national television here last week that the gulf crisis is a chance for this country to shake off its post-war isolationism. To date, though, Kaifu's efforts to make Japan an active partner in the U.S.-led alliance against Iraq have prompted scorn overseas and squabbles at home.

Japan imports all of its oil, about 70 percent of it from the Middle East. But the money and manpower Japan has promised to assist allied nations lined up against Iraq is less than that offered by other, less populous and less prosperous countries.

That disparity has prompted angry commentary from politicians and editorial writers around the world. U.S. Treasury Secretary Nicholas Brady is scheduled to arrive here Friday and is expected to ask for more aid for the gulf effort.