Iran vowed to defend itself after the United States military joined Israel’s war against Iran early Sunday morning by dropping bombs and firing missiles at three key nuclear sites in the country, prompting fears that the American attack could lead to more dangerous escalations across the Middle East.

President Donald Trump says the U.S. military struck three sites in Iran, directly joining Israel ’s effort to decapitate the country’s nuclear program in a risky gambit to weaken a longtime foe amid Tehran’s threat of reprisals that could spark a wider regional conflict.