Chinese customs officers have stopped a container of United States bourbon whisky they say contains too much fusel oil, a decision Washington may challenge, diplomats said yesterday. Fusel oil is a mixture of amyl alcohols, propanol and butanol formed as a by-product of alcoholic fermentation. The bourbon contained a level of fusel oil that exceeded the Chinese standard. Scotch whisky and Cognac brandy usually contain no fusel oil or less than the Chinese standard. It was not immediately clear which bourbon was involved, but Jim Beam and Jack Daniels are the best known in China. Diplomats said it was too early to say whether it would only concern this shipment or whether it would result in a halt to all bourbon imports. If it were the latter, it could become a trade issue. 'Americans have been drinking bourbon for more than 200 years with no visible harm to their health,'' one diplomat said. AAThe Chinese have not enforced this standard until now. They may have taken the standard from Europe.'' An American businessman L said that, since China joined the World Trade Organisation in December, most government ministries had worked hard to comply with WTO standards, especially in services and manufacturing. 'But, in agriculture, we have seen the increasing use of standards and other non-tariff measures in the last six months. The ministry is trying to protect the interests of local growers, even when domestic prices are higher than international ones. Agriculture is a sensitive area,'' he said. 'Domestic grain policy, with the state as a monopoly buyer, has not been a success, with the state holding millions of tonnes of low quality grain, paying a huge and unsustainable subsidy and farmer incomes declining. There will have to be a major adjustment.''