The United States defence secretary has accused Iran of being the “world’s biggest state sponsor of terrorism”, capping off a week of rising tensions between the two countries.

James Mattis warned that the world would not ignore Iranian activities, which he said were helping destabilise the entire Middle East.

"We have seen their [Iran's] misconduct, their misbehaviour, from Lebanon and Syria to Bahrain and to Yemen and it's got to be addressed at some point," he told reporters on Saturday in Tokyo, where he is on his first official foreign visit. “I think it is wise to make certain that Iran recognises that what it is doing is getting the attention of a lot of people.”