Russian collaboration with in Iran in the energy sphere may complicate Russian-American relations. This opinion was voiced by US Ambassador to Russia Alexander Vershbow on Friday, January 17 at a press conference 'Russian-American Relations. Joint Efforts in the Struggle with International Terrorism.' According to Vershbow, the US is deeply concerned by the fact that Russia is collaborating with Iran over nuclear developments. The ambassador explained that the US believes that this cooperation could help Iran to build a nuclear weapon. Vershbow added that his government admits that this collaboration is taking place within the IAEA's guidelines. However, he expressed the hope that Russia 'will tighten controls over the export of this technology.'