At a ceremony for some 600 soldiers headed for Iraq in Japan's first troop dispatch to a combat zone since World War II, Koizumi stressed the humanitarian nature of the mission, which was nonetheless slammed by protestors.

"You are not going to war and you are not going to participate in a mop-up operation against terrorists," Koizumi told rows of troops in green fatigues and berets at a building in Asahikawa base in snowy northern Japan.

"You will not use force, and you are not going to participate in combat," he said. "Your activities are to help the Iraqi people have hope and rebuild their country by themselves."

Students braving the cold shouted at cars entering and leaving the base Sunday, "Stop the dispatch!" and "Koizumi, quit!", while right-wing trucks blared from speakers, "Work hard, Self-Defense Forces!"

Koizumi said he felt more and more Japanese supported the dispatch, saying he hoped Japan would be remembered by future Iraqi leaders as "extending a hand when their country was suffering".

"Political opinion is divided, but I believe that even among those opposed, there are many Japanese who are cheering on the activities of the Self-Defense Forces," he said.

Koizumi's speech came two days before 80 to 90 of the ground troops' main contingent of 600 were to head the southern Iraqi town of Samawa to set up camp, following a 39-strong advance team that left in mid-January.

It was also was aimed at countering charges that the dispatch violates Japan's pacifist constitution, which forbids the use of force in settling international disputes.

Opposition and some ruling party lawmakers boycotted a lower house parliamentary vote late Friday authorizing the main contingent's dispatch.

But a poll last week showed public opposition to the move fell to 47 percent, even with those supporting it and down from about two-thirds opposed in September.

Former leader of the main opposition Democratic Party of Japan, Yukio Hatoyama, told a TV Asahi talk show Sunday the rising support only reflected concern for Japanese troops.

"Despite the fact that the law allowing their dispatch is terrible, if they are going, all Japanese including myself want the officers to do a good job," he said.

The upper house is expected to formally approve the dispatch with the ruling coalition's overwhelming majority this week.

Several Japanese military contingents have already been in Iraq or Kuwait on exploratory missions since December. On Friday three air force cargo planes flew into Kuwait to beef up Japan's mission.

All 600 ground troops should be in place by the end of March, with logistic support from around 400 air force and naval personnel in the region.

Although Japanese troops in Iraq are armed and legally allowed to return fire in self defense, they have been afforded protection by the Dutch military.

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