Japan must face its share of the dangers of rebuilding Iraq, Prime Minister Junichiro Koizumi said Monday while asking his nation to back his plans to send troops on an aid mission.

After Koizumi spoke, an advance team of Japanese soldiers (search) crossed into southern Iraq, beginning this country's most dangerous overseas military operation since World War II. The Japanese advance group, escorted by Dutch forces, moved overland from the U.S. military base Camp Virginia (search) in the Kuwaiti desert to southern Iraq.

With recent polls showing most voters opposing the dispatch, the prime minister made it a centerpiece of his policy speech marking the beginning of the five-month Parliamentary session.

"We won't have fulfilled our responsibility as a member of the international community if we contribute materially and leave the manpower contribution up to other countries because of the possible dangers involved," Koizumi said.

"Japan's development and prosperity depends on world peace and stability. We will aggressively contribute to the rebuilding of Iraq."

Koizumi's determination to deploy some 1,000 navy, air and ground troops to help rebuild Iraq despite deep public reservations reflects a shift in the government's attitude since the 1991 Gulf War, when Tokyo shouldered a big portion of the financial burden but sent no soldiers.

Criticized at home and abroad for relying on "checkbook diplomacy" during that war, Koizumi and his allies in the ruling Liberal Democratic Party (search) have been eager to contribute Japanese troops to back the United States, its most important ally.

Since late 2001, Japan's navy has provided support to the U.S. campaign against terror in Afghanistan.

The 1,000-strong Japanese contingent, expected to arrive in Iraq by March, will help purify local water supplies, rebuild schools and provide medical care in the country's south. They will carry arms for self-protection but their role will be noncombatant.

The mission puts Japan's soldiers in a combat zone for the first time since World War II.

But the public is less enthusiastic, with two recent newspaper polls showing a majority of those questioned opposing the deployment.

To counter allegations the dispatch violates Japan's war-renouncing constitution, Koizumi said the mission adheres to the spirit of the document's preamble committing Japan to strive for an "honorable place in an international society."

Still, critics worry Japanese soldiers could be drawn into combat, violating the constitution's body.

The Democratic Party, the largest opposition bloc, vows to debate the dispatch in the 150-day Parliament session, with hopes of gaining political ground ahead of key upper house elections in July.

Koizumi's foreign minister later told lawmakers that Tokyo would funnel the $1.5 billion in aid it already pledged for Iraqi reconstruction into rebuilding power, water and education infrastructure.

"The lives of the Iraqi people have deteriorated for a quarter-century under a repressive regime," Yoriko Kawaguchi said. "We need to provide Iraqis with aid that they truly need and appreciate so they can regain a normal way of life."

The U.S. military has hailed the imminent arrival of Japanese humanitarian troops as a "tremendous contribution."

Koizumi also is building momentum for a historic rethinking of the constraints placed on Japan's military by the 1947 constitution, written by the United States. His party is drafting a revision of the document, which has never been amended.