Iran threatened on Tuesday (Sep 29) to attack infrastructure around the Middle East, intensifying its rhetoric as it awaits a formal response from Washington on a new plan to reopen the Strait of Hormuz.

US President Donald Trump has already dismissed the proposal from Tehran, but Iran's foreign minister said on Monday that he was expecting a formal response from American officials within a day.

Fighting has subsided in recent weeks, though Tehran has continued to target ships in the strait, with Washington falling back on an economic pressure campaign instead of further military action.

Iran's chief negotiator Mohammad Bagher Ghalibaf on Tuesday threatened new attacks, saying no infrastructure in the region would be safe if his country's security was not guaranteed.

"In a region where we cannot sell oil, no one else will sell oil either; or if our security is not guaranteed, no infrastructure will remain safe," Ghalibaf, who is also Iran's parliament speaker, said according to a video released by state TV.

Iran has maintained a blockade on commercial shipping through Hormuz since the war began in late February with US-Israeli strikes on the Islamic republic.

The shipping route carried a fifth of the world's oil and liquefied natural gas before the conflict began.

The US military has been maintaining a counterblockade of Iran's ports in an effort to prevent Tehran from exporting oil.