Secretary of State Mike Pompeo has said the US is imposing the “strongest sanctions in history” on Iran.

In a speech in Washington, the top American diplomat said Iran would be “battling to keep its economy alive” after the sanctions took effect.

He said he would work closely with the Pentagon and regional allies “to deter any Iranian aggression”.

Earlier this month, President Donald Trump took the US out of the landmark 2015 Iran nuclear deal.

In his first major foreign policy speech as secretary of state, Mr Pompeo unveiled the administration’s “Plan B” for countering the Islamic republic on Monday.

“We will apply unprecedented financial pressure on the Iranian regime,” he said.

“The leaders in Tehran will have no doubt about our seriousness.

“Iran will never again have carte blanche to dominate the Middle East.”