President Joe Biden has pledged that the US is “prepared to use all elements of its national power” to stop Iran from getting a nuclear weapon.
Mr Biden made the declaration with Israel’s Prime Minister Yair Lapid on the second day of his visit there.
Israel considers the Iranian nuclear programme to be its greatest threat, though Iran insists it is peaceful.
The president will hold talks with Palestinian officials on Friday before a controversial visit to Saudi Arabia.
Mr Biden outlined a series of strategic commitments underpinning the US relationship with Israel.
He also pledged that the US would “work together with our other partners to confront Iran’s aggression and destabilising activities”, including Iran’s use of “terrorist organisations such as Hezbollah, Hamas and Palestinian Islamic Jihad.”
The US and Israel have long accused Iran of state-sponsored terrorism in the Middle East and further afield. Iran provides funding, training and weapons to Lebanon’s powerful Hezbollah movement, and the Palestinian groups Hamas and Islamic Jihad in the Gaza Strip.
Iran denies that it sponsors terrorism and says the organisations it backs are resistance groups fighting Israeli and US aggression.