While the U.S. insists it is not involved in strikes on Iran, American officials have confirmed military forces have been helping to intercept Iranian missiles fired at Israel.

Israel's onslaught on Iran appeared to enter a new phase Sunday in what has been described as the heaviest period of attacks yet.

All night people in Israel have been braced for more rockets. Just before 01:00 the Israeli military announced that it was striking missile sites in Iran, and instructed residents to move closer to shelters. Four hours later the response came – with what felt like the largest barrage so far of this conflict.

The conflict, the most intense fighting between the two countries in decades, has been met in the United States with feelings of “frustration and helplessness,” as well as heartbreak.

Israel and Iran have continued to trade heavy missile strikes overnight as Donald Trump threatens to respond 'at levels never seen before' if Tehran attacks US bases.Posting on Truth Social, the US president said his forces had “nothing to do with the attack on Iran,

The push to do a deal on the country’s nuclear program could be revived, even after the Israeli strikes scuppered the latest round of talks.

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.