TOKYO - Japan said Monday it was considering whether a pre-emptive strike on the North's missile bases would violate its constitution, suggesting it could take stronger action against the nation if the U.N. Security Council rejects its resolution calling for sanctions.

Japan was badly rattled by North Korea's missile tests last week and several government officials openly discussed whether the country ought to take steps to better defend itself, including setting up the legal framework to allow Tokyo to launch a pre-emptive strike against Northern missile sites.

"If we accept that there is no other option to prevent an attack ... there is the view that attacking the launch base of the guided missiles is within the constitutional right of self-defense. We need to deepen discussion," Chief Cabinet Secretary Shinzo Abe said.

Japan's constitution currently bars the use of military force in settling international disputes and prohibits Japan from maintaining a military for warfare. Tokyo, however, has interpreted that to mean it can have armed troops to protect itself, allowing the existence of its 240,000-strong Self-Defense Forces.

Despite resistance from China and Russia, Japan has pushed for a U.N. Security Council resolution that would prohibit nations from procuring missiles or missile-related "items, materials goods and technology" from North Korea. A vote was possible in New York later Monday.

"It's important for the international community to express a strong will in response to the North Korean missile launches," Abe said. "This resolution is an effective way of expressing that."

China and Russia, both nations with veto power on the council, have voiced opposition to the measure. Kyodo News agency reported Monday, citing unnamed Chinese diplomatic sources, that China may use its veto on the Security Council to block the resolution.

The United States, Britain and France have expressed support for the proposal, while Japanese Foreign Minister Taro Aso has said there is a possibility that Russia will abstain.

South Korea, not a council member, has not publicly taken a position on the resolution, but on Sunday Seoul rebuked Japan for its outspoken criticism of the tests.

"There is no reason to fuss over this from the break of dawn like Japan, but every reason to do the opposite," a statement from President Roh Moo-hyun's office said, suggesting that Tokyo was contributing to tensions on the Korean Peninsula.

Meanwhile, a Chinese delegation including the country's top nuclear envoy -- Vice Foreign Minister Wu Dawei -- arrived in North Korea on Monday, officially to attend celebrations marking the 45th anniversary of a friendship treaty between the North and China.

Talks have been deadlocked since November because of a boycott by Pyongyang in protest of a crackdown by Washington on the regime's alleged money-laundering and other financial crimes.

Beijing has suggested an informal gathering of the six nations, which could allow the North to technically stand by its boycott, but at the same time meet with the other five parties -- South Korea, China, the U.S., Japan and Russia. The U.S. has backed the idea and said Washington could meet with the North on the sidelines of such a meeting.

In Tokyo, U.S. Assistant Secretary of State Christopher Hill met with Aso on Monday as part of a tour through the region to coordinate strategy on North Korea. Hill has emphasized the need for countries involved to present a united front.

"We want to make it very clear that we all speak in one voice on this provocative action by the North Koreans to launch missiles in all shapes and sizes," Hill said. "We want to make it clear to North Korea that what it did was really unacceptable."