The primary drawback of using conventionally tipped ballistic missiles is that they are virtually impossible for radar warning systems to distinguish from nuclear-tipped missiles. This leaves open the likelihood that other nuclear-armed countries might mistake it for a nuclear launch which could provoke a counterattack. For that reason among others, this project raised a substantial debate before US Congress for the FY07 Defense budget, but also internationally. Russian President Vladimir Putin, among others, warned that the project would increase the danger of accidental nuclear war. "The launch of such a missile could ... provoke a full-scale counterattack using strategic nuclear forces," Putin said in May 2006.