Friday, March 10 2006 18:29 Hrs (IST) - World Time -

Washington: The United States will seek a 'strong' UN Security Council statement against Iran's nuclear programme, the White House said as Secretary of State Condoleezza Rice called Iran Washington's biggest challenge.

US Defence Secretary Donald Rumsfeld also said that the United States had no plans to attack the Islamic republic but he warned that US forces would take action to stop Iranian forces infiltrating Iraq.

Amid mounting tensions over the nuclear standoff, White House spokesman Scott McClellan said the United States still wants a diplomatic solution to the nuclear dispute.

"We are pursuing a diplomatic resolution to the nuclear issue when it comes to Iran," McClellan told reporters

. "The first step in the Security Council will not be looking at sanctions, it will be looking at the possibility of a strong presidential statement laying out very clearly for the regime what it needs to do and calling on the regime to take certain steps," he said.

US officials have said they expect the UN Security Council to start debating Iran next week, after a report by the International Atomic Energy Agency (IAEA) was referred to the world body.

Washington has already laid out a strategy which would take gradual steps toward sanctions, in a bid to get greater international support for any UN action taken.

Secretary of State Rice said Iran had become a key threat to world peace as she sought Congress backing for a package to promote democracy in the Islamic republic.