President Donald Trump has warned that countries continuing to do business with Iran could face a 25% tariff on trade with the United States, following a deadly crackdown on anti-government protests.

Officials have told CBS News, a US partner of the BBC, that Mr Trump has also been briefed on a range of military and covert options regarding Iran, including long-range missile strikes, as well as cyber and psychological operations. 

In recent days, the president has suggested that a military intervention could be possible if protesters are killed. His national security team is scheduled to meet later to discuss potential responses.

Meanwhile, Iran’s foreign minister has said Tehran remains open to talks with Washington, while also emphasising that the country is “prepared for war”.

The crackdown in Iran has already claimed at least 648 lives, according to a human rights group, which has cautioned that the true death toll could be much higher.

 A days-long internet blackout is hampering verification of events in the country, and most international media are unable to report from Iran.