Two years after the United States helped disrupt a notorious nuclear smuggling ring, the Bush administration has hobbled a Swiss effort to prosecute three of the alleged leaders by failing to share critical information, an American nuclear expert and Swiss law enforcement officials said yesterday. Switzerland’s federal prosecutor made at least four separate appeals for U.S. help over the past year, asking for access to documents and other evidence linked to the nuclear black market run by the Pakistani scientist Abdul Qadeer Khan. In that time, the Swiss have received no assistance, or even a reply, a spokesman for the prosecutor said. Full Story