Japan has begun studying the feasibility of easing rules on the use of weapons by Self-Defense Forces troops taking part in logistic support for the expected U.S. military operation against terrorism, government sources said.

The government is considering allowing troops to use weapons when deemed "necessary to carry out duties" under a soon-to-be-submitted bill authorizing the SDF to provide logistic support to U.S. military action against the terrorists connected with the Sept. 11 attacks in the United States, they said Saturday.

The government previously envisioned allowing the troops to only use weapons to protect themselves and their colleagues, a restriction imposed by existing laws on troops taking part in U.N. peacekeeping operations or logistic support of U.S. forces in the event of an emergency in "areas surrounding Japan."

The use of weapons by SDF troops has been strictly limited so that it does not infringe on Japan's constitutional ban on the "use of force as a means of settling international disputes."

The relaxation of the restrictions would allow the troops to use weapons even if they were not attacked.

It is still uncertain, however, whether the measure is included in the bill to be submitted to the Diet because New Komeito , one of the two coalition allies of the ruling Liberal Democratic Party, remains cautious.

New Komeito is concerned that altering the provision may allow the troops to easily resort to the use of weapons, they said.

Defense Agency and SDF officials said they have asked for the relaxation in the rules. , arguing the antiterrorism operation may be significantly more dangerous than U.N. peacekeeping missions.

Under the bill, the SDF is supposed to provide support such as transportation, supply and medical treatment in areas outside battlefields to U.S. forces engaged in antiterrorism operations.

The bill is expected to be proposed to the Diet during a 72-day extra session that convenes Thursday.

The new legislation is being prepared because the 1999 law on procedures during an emergency in areas surrounding Japan is difficult to apply to activities in Afghanistan, Pakistan or the Indian Ocean.