The beheading of a Japanese hostage in Iraq renewed pressure on Prime Minister Junichiro Koizumi (search) to withdraw his country's troops, as the opposition blamed his pro-U.S. policy for the slaying.

Japanese officials said fingerprint tests proved a decapitated body, wrapped in an American flag, found in Baghdad was that of backpacker Shosei Koda (search), who had been held by Al Qaeda-linked militants demanding Tokyo withdraw its 500 troops from the southern city of Samawah.

Koizumi, who must soon decide whether to extend Japan's deployment beyond a Dec. 14 deadline, called the killing a "brutal, inhuman act."

He said that Koda's murder and the question of the deployment were separate issues. But officials said an extension of the mission hadn't been decided, and Koizumi refrained from making any commitments — sparing him embarrassment if he ultimately decides to withdraw.

Japan's largest opposition party charged that Koizumi's pro-U.S. policy had made Japan a target of terrorism.

"It's a fact that if Japan had not dispatched troops, this incident would not have happened. I will strongly push ... so that it is not extended and the troops are withdrawn," said Democratic Party leader Katsuya Okada. He had opposed sending the troops, who are on a non-combat mission to supply clean water and medical aid and fix roads and schools.

Losing Japan would be a minor setback to relief efforts in Iraq but a major political blow to Washington's efforts to hold together its international coalition.

Koizumi has been one of Washington's firmest backers in Iraq. Though Japan's constitution bans the country's troops from engaging in combat, Tokyo backed the U.S. case for invasion and sent some 1,000 troops to Iraq and neighboring countries to help reconstruction efforts.

Japanese Vice Foreign Minister Shuzen Tanigawa arrived in Kuwait Sunday and told reporters there that he will be accompanying Koda's body to Tokyo.

Koda, who left Japan in January for a yearlong trip starting in New Zealand, had told people he wanted to see Iraq. He entered the country on Oct. 21 and was last seen two days later trying to return to Jordan from a Baghdad bus terminal.

Although Japan's presence in Iraq isn't popular at home, many Japanese blamed Koda for his own death.

"He went there after ignoring repeated travel warnings by the government and I saw no sign he was moved by ideology or principle ... He seemed like he just wanted to see it," said Hiroyuki Miyamoto, a mobile phone company employee. "If you go that far, I feel you're responsible for what happens."

In a statement after the confirmation of his death, Koda's family said: "We thank everyone for their trouble. We pray that the Iraqi people will find peace."

Koda's ordeal began on Tuesday, when an al-Qaida-linked group led by Jordanian terrorist Abu Musab al-Zarqawi threatened in a video on a militant Web site to behead him within 48 hours unless Japan withdrew its troops from Iraq. Koizumi quickly rejected it and frantically launched diplomatic efforts to win his release.

Iraqi officials found Koda's decapitated body Saturday, dumped on a Baghdad street known for insurgent activity. Associated Press Television News videotape showed the severed head with the hostage's long black hair and features.

It was the first slaying of a Japanese hostage in Iraq. Five Japanese civilians were taken hostage there in April but were released unharmed.

Washington denounced the killing and commended Tokyo for not bowing to terrorism.

"We strongly condemn this heinous crime. There is no justification for acts like this," U.S. Ambassador to Japan Howard H. Baker Jr. said in a statement. "We strongly support the Government of Japan's rejection of terrorist demands and deeply appreciate its steadfast commitment."

More than 160 foreigners have been kidnapped in Iraq this year and at least 33 of them have been killed.

At least 10 foreigners are still in the hands of kidnappers — including two French journalists held for more than two months, two women — Margaret Hassan, the head of CARE international in Iraq, and Pole Teresa Borcz Khalifa — and two truck drivers, a Bangladeshi and a Sri Lankan.