The United States is the main international backer of Israel, Iran's biggest regional foe. It is also a close ally of Sunni Gulf monarchies which for years pursued their own rivalry with the Islamic Republic, seeing it as their main regional threat.

Tehran said American bases in the Middle East could face reprisals if the U.S. helped repel Iranian attacks on Israel.

Iran's top diplomat Abbas Araghchi said Saturday that Israel's strikes on his country were undermining nuclear talks with the United States. Araghchi, in a call with Russia's Foreign Minister Sergei Lavrov,

Iraq on Saturday called on the United States to prevent Israeli aircraft from breaching Iraqi airspace to carry out attacks against Iran, citing bilateral agreements and international law.

Israel’s leader and President Trump appeared to bet they can persevere, but other world leaders warned of unintended outcomes in a volatile region.

National security experts warn that Israel's attack on Iran shows why Chinese land and asset purchases in the U.S. pose a significant threat to American security.

The United States has pulled some diplomatic staff and military families out of the Middle East, citing unspecified regional security risks.

Interviews with half a dozen senior Iranian officials show that they were not expecting Israel to strike before another round of talks.