US President George W. Bush warned on Thursday that allowing Iran to obtain nuclear weapons would be "an unforgivable betrayal of future generations."

"Permitting the world's leading sponsor of terror to possess the world's deadliest weapon would be an unforgivable betrayal of future generations," Bush said in remarks prepared for delivery to the Israeli parliament.

"America stands with you in breaking up terrorist networks and denying the extremists sanctuary. And America stands with you in firmly opposing Iran's nuclear weapons ambitions," said Bush, who is on a three-day visit to Israel.