Bush says Iran may be greatest challenge to US

US PRESIDENT George Bush has said Iran may pose the greatest challenge to the United States.

He added that diplomatic moves to thwart the Islamic nation's nuclear programme must prevail to avoid confrontation.

In a 49-page national security report, the president reaffirmed the strike-first, or preemptive, policy he first outlined in 2002.

Diplomacy is the US preference in halting the spread of nuclear and other heinous weapons, Mr Bush said.

Meanwhile, Iran's top nuclear negotiator said Tehran was ready to open talks with the US over Iraq, marking a major Iranian foreign policy shift.

This is the first time since the 1979 Islamic Revolution that Iran is officially calling for dialogue with the US, which it has repeatedly condemned as "the Great Satan".

Ali Larijani told parliament in Tehran: "To resolve Iraqi issues and help establishment of an independent and free government in Iraq, we agree to (talks with the US)."

It was not immediately clear what Mr Larijani was talking about. But the US has repeatedly accused Iran of meddling in Iraq's affairs, and even sending weapons and fighters to help the insurgency.

Iran also has expressed grave concerns about the prospect of more violence in Iraq, where bloody sectarian fighting and reprisal killings have broken out in recent weeks.

Mr Larijani did not address the nuclear issue.

The US responded that it was prepared to talk with Iran about Iraq, but said any discussions must be restricted to that topic and not include other contentious subjects.

Zalmay Khalilzad, the US ambassador to Iraq, is authorised to talk with Iran about Iraq, much as the US has talked with Iran about issues relating to Afghanistan, White House press secretary Scott McClellan said.

However, the security report had harsh words for Iran. It accused the regime of supporting terrorists, threatening Israel and disrupting democratic reform in Iraq.

The White House released the National Security Strategy report in conjunction with a speech by Bush national security adviser Stephen Hadley, at the US Institute of Peace.

Reaffirming his preemptive policy, Mr Bush wrote: "If necessary, however, under long-standing principles of self-defence, we do not rule out the use of force before attacks occur even if uncertainty remains as to the time and place of the enemy's attack.

"When the consequences of an attack with weapons of mass destruction are potentially so devastating, we cannot afford to stand idly by as grave dangers materialise.

"The place of preemption in our national security strategy remains the same."