Israeli Prime Minister Ehud Olmert has said drastic measures are needed to stop Iran obtaining nuclear weapons.
Speaking to the main pro-Israel lobby in the US, he said Iran must be shown there will be devastating consequences if it did develop such weapons.
The US and others have accused Iran of building a nuclear arms capability. Tehran says its programme is peaceful.
Mr Olmert’s US visit comes as he faces pressure at home over corruption allegations, which he denies.
Mr Olmert is expected to discuss the Iranian nuclear issue in talks with President George W Bush on Wednesday.