The war in the Middle East spiraled further Monday as Israel and the U.S. pounded Iran in a campaign that U.S. President Donald Trump said would likely take several weeks. Tehran and its allies hit back against Israel, neighboring Gulf states and targets critical to the world’s energy production.

The intensity of the attacks, the killing of Iranian Supreme Leader Ayatollah Ali Khamenei, and the lack of any apparent exit plan set the stage for a prolonged conflict with far-reaching consequences. Safe havens in the Mideast like Dubai have seen incoming fire; hundreds of thousands of airline passengers are stranded around the globe; oil prices shot up; and U.S. allies pledged to help stop Iranian missiles and drones.

With no sign of the conflict abating anytime soon, Trump said Monday that the operations are likely to last four to five weeks but that he was prepared “to go far longer than that.”

He said U.S. forces were determined to destroy Iran’s missile capabilities, wipe out its naval capacity, stop the country from obtaining a nuclear weapon and ensure that Iran cannot continue to arm and fund allied groups like Lebanon's Hezbollah, which fired missiles at Israel, drawing retaliatory airstrikes.

"This was our last, best chance to strike -- what we’re doing right now -- and eliminate the intolerable threats posed by this sick and sinister regime,” Trump said.

Iran has long threatened, if attacked, to drag the region into total war, including targeting Israel, the Gulf Arab states and the flow of crude oil crucial for global energy markets. All of these came under attack on Monday.

The chaos of the conflict became apparent when the U.S. military said Kuwait had “mistakenly shot down” three American F-15E Strike Eagles while Iran was attacking with aircraft, ballistic missiles, and drones. U.S. Central Command said all six pilots ejected safely and are in stable condition.

The Gulf state of Qatar meanwhile said its air force had shot down two Iranian Sukhoi Su-24 bombers.

Israel and the U.S. bombed Iranian missile sites and targeted its navy, claiming to have destroyed its headquarters and multiple warships. As several airstrikes hit Iran’s capital of Tehran, the top security official Ali Larijani vowed on X: “We will not negotiate with the United States.”

The death toll grew on all sides. The Iranian Red Crescent Society said that the U.S.-Israeli operation has killed at least 555 people. In Israel, where several locations were hit by Iranian missiles, 11 people were killed. The Iranian-backed Hezbollah militant group also targeted Israel, which responded with strikes on Lebanon, killing more than two dozen people. Meanwhile, four American troops have been killed, and three people were reported killed in the United Arab Emirates and one each in Kuwait and Bahrain.