Fresh U.S. military action against Iran and President Donald Trump’s declaration that the interim accord is effectively finished pushed oil prices higher while U.S. stock futures remained in positive territory.

Any renewed attacks would follow strikes by both the U.S. and Iran following the downing of a U.S. helicopter.

Trump ordered fresh strikes on Iran on July 8 and warned that the US would respond with much worse if Tehran continued attacking ships passing through the Strait of Hormuz, one of the world's busiest oil shipping routes.

The US military launched a new round of strikes against Iran on Wednesday, following President Donald Trump's assertion that the fragile ceasefire between the two countries was over. Trump warned that the attacks could get "much worse" if Iran perpetrated further attacks on ships in the Strait of Hormuz.

Trump had said that the ceasefire with Iran is "over" after Washington launched strikes on the country overnight, to which Iran responded by targeting US bases in the Gulf.

Iran says it attacked sites linked to the US military in Kuwait, Bahrain and Qatar after US bombarded targets in Iran.

The United States launched a fresh wave of military strikes against Iran on Wednesday, targeting what it described as Tehran's ability to threaten shipping through the strategically vital Strait of Hormuz.