"The United States is not seeking war with the Iranian regime, but we are fully prepared to respond to any attack, whether by proxy, the Islamic Revolutionary Guard Corps or regular Iranian forces," Bolton said in a statement.

Washington has piled on sanctions on Iran over its nuclear program this week and designated IRGC as a terrorist organization in April.

Washington announced sanctions against Iran’s nuclear power plant at Bushehr and a ban on exports of heavy water and any further uranium enrichment on Friday.

In April, the Trump administration said it would not renew exemptions granted last year to buyers of Iranian oil in line with its plan to bring the Islamic Republic’s crude exports to zero.

The move was criticized by European countries who said that Tehran is adhering to the nuclear agreement that Washington ditched last year. 

Tehran has been responding to every US action with statements full of resilience and blasting Washington's "bulling." Iran's deputy foreign minister said on Wednesday that if fighting breaks out between Iran’s Revolutionary Guards and US CENTCOM forces in the Persian gulf, it is Washington who would be held responsible.