"I am not going to allow this to happen. And no future American president can allow it, either," Bush said in a speech on the war against terrorism.

"Their choice is increasingly isolating the great Iranian nation from the international community. It is time for Iran's leader to make a different choice," Bush said.

The United States has accused Iran of trying to develop nuclear weapons under the cover of civilian nuclear programs. Iran has said that its nuclear programs are for peaceful purposes only.

The United Sates is now seeking to impose sanctions on Iran for its refusal to comply with a UN Security Council resolution demanding Teheran stop uranium enrichment.