Hardline President Mahmoud Ahmadinejad on Thursday warned European countries not to follow the US lead in imposing unilateral sanctions against his country, state radio reported. Ahmadinejad threatened unspecified retaliation by Iran if Europe followed in the footsteps of the United States, which last week announced sanctions against the Islamic state. "If they plan to cooperate with the enemy of the Iranian nation, we cannot interpret this as a friendly behavior. We will show reaction," the radio quoted Ahmadinejad as saying. The US measure bans dealings with a host of companies connected to Iran's Revolutionary Guards, an elite force that has extensive business holdings in oil, construction and other sectors. It also prohibits American companies from working with the Guards-linked Iranian companies and puts pressure on international firms and banks not to deal with them as well.