East Asian countries have committed 4,500 troops to Iraq, despite increasingly vocal calls for them to be withdrawn or not deployed. South Korea had promised the bulk, 3,600, which would have made its contingent the third biggest in Iraq after the US and Britain. But Seoul yesterday backed out of plans to allow its troops to serve in northern Iraq. The South Korean government cited a disagreement with the US over its proposal to conduct 'joint offensive operations' in the war-torn country. The South Korean Defence Ministry said it still planned to send its promised 3,600 troops to Iraq - fewer than the US is thought to have requested - but would look for alternative sites where they could operate independently. Among other nations, two-thirds of Japan's pledged 570 soldiers are already in Iraq, as are 96 troops, police and medical workers from the Philippines. Singapore has about 200 soldiers on a landing craft providing security in the Persian Gulf. The nations' overwhelming reason to militarily back the American effort was because of a strong sense of allegiance, a US expert on the region, Stephen Bosworth, said yesterday during a visit to Hong Kong. 'By and large, the countries are sending troops to Iraq as a gesture of support for the US, their major ally,' Mr Bosworth, the dean of Tufts University's Fletcher School of Law and Diplomacy and a former US ambassador, said. 'They're not doing it primarily out of their own definition of narrow self-interest. They have a broader agenda.' American troops are either based or involved in training in all of the countries. The presence is strongest in South Korea, which hosts 37,000 US service people as a deterrent against North Korea. Yonsei University professor of international relations Lee Jung-hoon said the alliance extended to a mutual defence treaty under which both countries promised to protect one another if threatened. Iraq and the US-led war on terrorism were an extension of that agreement. But the countries also had a deeper bond based on blood - American soldiers had lost their lives for South Korea during the Korean war, while South Koreans had done the same for the US in the Vietnam war. Japan has long realised its global position, but has used the US request for help to make its biggest military deployment since 1945. Along with the troops, eight aircraft, including three C130 transport planes, have been despatched. Plans have also been announced to send up to six ships. The decision is controversial because of Japan's pacifist constitution, high anti-war sentiment among Japanese and rising agitation for removal of the 40,000 US troops based in the country. The Philippines and Singapore have been staunch supporters of the wars on terror and in Iraq. In return, the US has provided the Philippines with military assistance and helped fight Muslim extremists, while last year it signed a free trade agreement with Singapore.