Japanese ships may help the US
Japan's military are currently prevented from any action other than self defence by the country's pacifist constitution.
But Prime Minister Junichiro Koizumi wants to relax the constitutional constraints to remove the ban on collective self-defence or aiding allies when they are attacked.
He repeated on Tuesday a pledge of non-combat support to the United States at a meeting with President George W Bush in Washington.
90% support US
The survey carried out by the Mainichi Shimbun newspaper suggested that 41% of respondents favoured allowing Japanese forces to engage in collective self-defence - up from 25% before the attacks.
It also suggested 90% support for co-operation with the US military campaign against terrorism, although the majority believe support should be limited to logistical aid and medical care.
A second poll in the Yomiuri Shimbun newspaper indicated 87% support for the US.
Both surveys, however, showed only 10% of respondents thought Japan's armed forces should take part directly in combat.
Constitutional changes
The surveys came as the government is preparing to enact revisions on Thursday of the Self Defence Forces Law. It wants to allow the Japanese military to protect US bases in Japan and other key facilities.
Legislation is also being prepared - with a deadline of late October - to allow Japanese forces to provide rearguard support such as medical services and transporting supplies.
Up to four Japanese ships, including a state-of-the-art destroyer are reported to be preparing to sail to rendezvous with a US fleet in the Indian Ocean.
The Japanese Government appears determined to avoid he humiliation it suffered during the Gulf War, when it contributed money but no troops and received little thanks from the participants.
But any constitutional changes freeing up Japan's military is sure to raise concerns among neighbouring countries who have previously suffered under Japanese wartime military aggression.