Iranian President Hassan Rouhani has threatened again to close the Strait of Hormuz, the passageway for nearly a third of all oil traded by sea.

State TV quoted Rouhani on Tuesday as saying that "if someday, the United States decides to block Iran's oil (exports), no oil will be exported from the Persian Gulf."

The strait at the mouth of the Persian Gulf is crucial to global energy supplies.

Rouhani also pledged that the US wouldn't be able to prevent Iran from exporting its crude oil.

Rouhani has made similar threats previously, especially after President Donald Trump threatened to decrease Iran's oil export to nil.

His threat was welcomed by many Iranian officials, including hard-liners such as Gen Qassem Soleimani, the commander of the Revolutionary Guard's powerful Quds Force.