"Today, instead of intimidating others, the Americans would do better to save their troops infected by the coronavirus," said Brigadier General Abolfazl Shekarchi, spokesman for Iran's armed forces.

His comments, in an interview with the semi-official ISNA news agency, came after Trump said on Twitter he had "instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea".

The Pentagon later said the US military considered the tweet a message to the Iranian regime, suggesting that no new orders had been issued to US Navy ships patrolling the Gulf.

"If the US is skilful and competent, they will withdraw their troops (from the Middle East) in order to save (the country) from the coronavirus disease... before mobilising all other forces in the US... to save the people from this major crisis hitting their country," Shekarchi said.

This renewed tension between longtime foes Iran and Washington comes after an incident last week in Gulf waters between US Navy ships and patrol boats of Iran's Islamic Revolutionary Guard Corps.

Washington accused the patrol boats of harassing US ships in international waters.

The Revolutionary Guards in turn accused the US of giving a "Hollywood" version of events and behaving "unprofessionally" in the Gulf.

Iran considers itself the guardian of the Gulf and opposes any western military presence in the channel, which is vital for global shipping and oil transport.