Updated

Japan's prime minister, a staunch U.S. ally in Iraq, refused on Wednesday to withdraw Japan's troops from the country, taking a tough stance in the face of demands by militants threatening to behead a Japanese hostage unless the soldiers leave.

The victim — a 24-year-old man said to have entered Iraq as a tourist — appeared in a video posted on a militant Web site Tuesday in which the Al Qaeda (search)-linked group led by Abu Musab al-Zarqawi vowed to kill him within 48 hours unless the demands were met.

"The Self-Defense Forces will not withdraw," Prime Minister Junichiro Koizumi told reporters as he visited sites in western Japan devastated by a typhoon. "I cannot allow terrorism and cannot bow to terrorism."

The hostage video was being shown repeatedly on the national broadcaster NHK, threatening to raise an uproar that could bring a new test for Koizumi. His pro-American stand on Iraq has been unpopular, with many Japanese fearing the presence in Iraq could draw Japanese troops into the fighting and prompt insurgents to target Japanese civilians.

When five Japanese were taken hostage in April, Koizumi also refused to give in to demands that the troops be withdrawn. All the hostages were freed unharmed, boosting Koizumi's popularity. Many Japanese criticized the hostages for putting themselves in danger by going to Iraq and imperiling government policy.

Tokyo has dispatched 500 troops to the southern Iraqi city of Samawah on a humanitarian mission to purify water and rebuild schools in support of U.S.-led reconstruction efforts.

In the new hostage drama, Koizumi told officials consider measures to free the hostage, Chief Cabinet Secretary Hiroyuki Hosoda said.

Koizumi spokesman Yu Kameoka said the government had set up a team to deal with the issue. The Foreign Ministry sent an envoy, Vice Minister Shuzen Tanigawa, to Jordan, as it did in the April hostage-takings.

Foreign Minister Nobutaka Machimura urged the hostage-takers to release the captive, identified as Shosei Koda, 24, saying he had nothing to do with Japan's deployment in Iraq.

"Mr. Koda is a private individual who is not related to the Self-Defense Forces or the government of Japan," Machimura said. "Japan is Iraq's friend and the entire Japanese nation demands the immediate release of Mr. Koda."

"I don't know why Mr. Koda entered Iraq, where the most dangerous situation prevails all over the country," Machimura said. "Our government has quite often asked people not to enter the nation."

Koda, of the southern city of Fukuoka, was identified by his father. Masumi Koda, 54, said his son left for New Zealand in January to travel.

Hiroshi Shinomiya, a film director, told NHK that he met Koda in Amman, Jordan, before he left for Iraq.

"Koda is a tourist," Shinomiya said. "I tried to stop him from going because it was too dangerous, but he said. `It's all right.' I don't think he was even carrying a cell phone."

The elder Koda appealed to the militants to free his son, saying he was only drawn to Iraq by a sense of sympathy for Iraqis.

"He simply wanted to encounter the pain felt by the Iraqi people and think about the future of the world," Koda told The Associated Press. "If you consider this and release him, he would become an adult, with a valuable future, who would seriously think about world peace."

The new crisis comes as a poll published by the national Asahi newspaper on Tuesday showed that 63 percent of Japanese oppose keeping their military in Iraq beyond this year, while 25 percent think the troops should stay.

Japan's troops are facing increasing hostility in Samawah, which was chosen for its relative safety. An unexploded mortar was discovered inside the Japanese base Saturday, the first time a projectile had been fired into the camp. There were no injuries.

The Foreign Ministry issued a new travel warning Wednesday, urging Japanese nationals not to enter Iraq.