THREE short sentences written by an American in 1947 have again returned to dog Japanese politics, and may have derailed attempts of Morihiro Hosokawa, the Prime Minister, to pass political reform laws before the end of the year. They are the anti-war provisions in Article 9 of the Japanese constitution, which were designed by US occupation authorities to prevent Japan rearming after the Second World War.

Under the provisions of Article 9, Japan 'forever renounces . . . the threat or use of force as means of settling international disputes' and also declares that 'land, sea and air forces . . . will never be maintained'.

But on Wednesday the Defence Minister, Keisuke Nakanishi, said the constitution was outdated and should be changed to allow full Japanese participation in United Nations peace-keeping missions. Although he was speaking at a private reception for his own party, the Japan Renewal Party, his remarks sparked a political uproar.

Japan already maintains a substantial army, navy and airforce, which are euphemistically called Self-Defence Forces. But the Japanese soldiers who took part in the UN operation in Cambodia this year were given special treatment to keep them out of dangerous situations - a concession that was criticised by other states.

Mr Nakanishi's view that Japan should accept the same responsibilities as any other nation in UN peace-keeping missions are shared by many politicians in Japan. 'While we respect the spirit of the peace constitution,' he said, it needed to be changed to 'correspond to reality'. But such is the taboo surrounding the constitution and Article 9 in particular that few politicians dare to speak their mind openly.

The comments were pounced on by the opposition Liberal Democratic Party (LDP) in the Diet (parliament), who have been seeking any excuse to disrupt Mr Hosokawa's attempt to clean up the political system. Their protests paralysed legislative business and forced Mr Hosokawa to ask Mr Nakanishi to resign on Thursday.

Yesterday Mr Hosokawa struggled to disassociate himself from the comments made by his defence minister and he apologised to the Diet. 'I would like to make clear my cabinet has no plan to take up any form of constitutional amendment on the political agenda and will continue to respect and uphold the current constitution,' he said.

The disruption came at a bad time for the government, whose political reform legislation was already being held up by deliberations on an emergency budget to stimulate the economy. Mr Hosokawa is also being forced to concentrate on the opening of Japan's rice market to keep in line with the Gatt trade liberalisation talks in Geneva.

Mr Hosokawa earlier pledged to resign if he could not get political reform laws through the Diet before the end of the year. This is now unlikely.