Yukio Hatoyama, leader of the Democratic Party of Japan, said Monday he understands the U.S. and British airstrikes against targets in Afghanistan but expressed concern over civilian casualties.

Hatoyama told reporters at DPJ headquarters the attacks are "based on the United States' individual right to self-defense" and that he has a "certain level of understanding" toward them as part of a campaign to eradicate terrorism.

"However, they must prevent ordinary citizens from being harmed," the leader of the opposition party said.

He called for caution in Diet deliberations on a bill that would allow Japan to provide rear-area noncombat support for the U.S.-led strikes.

The ruling coalition has demanded swift enactment of the bill following the attacks launched late Sunday. Prime Minister Junichiro Koizumi urged the opposition parties to drop their objection to it.

The bill, approved by the Cabinet and submitted to the Diet on Friday, would allow Japan to dispatch the Self-Defense Forces to provide logistic support such as medical services and transport of supplies.

"This situation had not been unforeseeable," he said. "We should not jump to the conclusion that the bill should be passed quickly, even without sufficient discussion. We need to take time."