Burma's attempts to pull off a propaganda coup by staging an international police heroin conference in Rangoon lay in tatters last night as the United States joined a widening boycott. Rangoon-based agents of the US Drug Enforcement Agency had been scheduled to attend the Fourth International Heroin Conference on February 23 until the State Department and other agencies intervened, diplomatic sources said. 'Given all the concerns that Washington has voiced about the Burmese military regime and the heroin trade, it would have been diplomatic suicide to let them take the initiative like this,' one source said. The US agency has forged solid links with Burma's junta over drug eradication efforts, but the State Department and CIA have voiced stern condemnation over the generals' role in the drug trade. The CIA claims Burma is the world's biggest opium producer and one of the largest manufacturers of heroin - a key supply for US dealers. The US withdrawal is expected to force Colombia - the world's biggest producer of cocaine and now a rapidly expanding heroin power - to take the moral high ground and stay away. The meeting appeared to be splitting the most strident foreign critics of the regime, but now opponents of the conference - a traditional bastion of law enforcement neutrality - appear to be getting the upper hand. The US will join Britain, Belgium, the Netherlands, Denmark and Luxembourg in the boycott, while France and Italy still intend to attend. Germany and Spain are undecided within the European Union, a body that enforces visa bans on senior Burmese officials. China, Vietnam, Thailand, and North Korea are among 23 nations that have indicated they will be at the conference. The US administration had been lobbied extensively by the Open Society Institute, which is backed by George Soros. It warned that holding such a conference in Rangoon was like staging a convention on terrorism in Tripoli or a seminar on women's rights in Kabul.