US Republican presidential candidate Mitt Romney says Israel and the United States should employ all measures to prevent Iran developing nuclear weapons.
Speaking during a visit to Jerusalem, Mr Romney said Iran was the most destabilising country in the world, the BBC reports.
He said the US recognised Israel's right to defend itself and that it was right for the US to stand with Israel.
In his speech, Mr Romney said the ayatollahs were "testing our moral defences" and the US would never look away from its passion and commitment to Israel.
He said the US had a "solemn duty and a moral imperative to deny Iran's leaders the means to follow through on their malevolent intentions".
After his meetings with Israeli officials, he went to Jerusalem's Western Wall, one of Judaism's holy sites.
The Republican presidential hopeful also met Palestinian Prime Minister Salam Fayyad, though not Palestinian President Mahmoud Abbas.
US President Barack Obama has focused on using sanctions to contain Iran's nuclear ambitions, the BBC says.