The president had opposed Israeli action against Iran but came to believe that Israel had reason to act and that the U.S. would have to lend some support.

Israel and Iran both have little incentive to stop and no obvious route to outright victory. Much depends on President Trump.

Israel and Iran exchange airstrikes targeting military sites and nuclear facilities, with Trump comments on the conflict and expressing optimism for diplomatic resolution.

President Donald Trump is desperate not to fight a war with Iran. But can he really avoid it? Compelling national security arguments and domestic political considerations mean it makes sense to stop short of direct US offensive operations in the long-dreaded conflict that Israel describes as a matter of preserving its own existence.

"The full strength and might of the U.S. Armed Forces will come down on you at levels never seen before," Trump warned.

Also looming over the meeting are President Trump's inflammatory threats to make Canada the 51st state and take over Greenland.

President Donald Trump said the United will come down on Iran “at levels never seen before” if the Middle Eastern country attacks.

Israel’s attack on Iran was long in the making – the result of years of meticulous planning by Israel and days of high-stakes talks between Tel Aviv and Washington, officials told CNN.