Former UN chief weapons inspector Hans Blix criticized the United States on Thursday for keeping open the possibility of military action to force changes in Iran's nuclear program. Blix was in Rome to take part in an international gathering of experts on nuclear proliferation that was held, coincidentally, during US President George W. Bush's three-day stop in the city. "The military threat may well be counterproductive," Blix said at a news conference. "It is more likely to strengthen the ranks in Iran." The veteran Swedish diplomat, who tried to avert the 2003 US-led invasion of Iraq because no weapons of mass destruction had been found by UN inspectors, said stronger economic sanctions are more likely to force Teheran to compromise on its nuclear program.