By Adam Brookes
BBC News Pentagon correspondent
Intelligence reports circulating in the US government claim that the al-Qaeda leadership has called upon Abu Musab al-Zarqawi to launch attacks in the US.
Officials have told the BBC that the group's leadership is reaching out to Iraq's most-wanted Islamic militant.
US intelligence says it has uncovered a communication from a top lieutenant of Osama Bin Laden destined for Zarqawi.
The organisation is said to have asked Zarqawi to expand his operations to include strikes inside the US.
But officials said there was no information regarding specific targets in the US.
Zarqawi leads an Islamist faction in Iraq blamed for some of the worst atrocities of the insurgency.
The intelligence services believe that Zarqawi allied himself with al-Qaeda last year.
But one official said it was still intriguing that al-Qaeda was reaching out to him.
He said it could be a measure of al-Qaeda's diminished capabilities that it was looking for other groups to carry out attacks in the US.
But, equally, he said the communication showed that al-Qaeda was still actively seeking to launch strikes against America.
It is not entirely clear why the US government has chosen to release such sensitive information, but the Bush administration has sought often to portray Iraq as what it calls the central front in the war on terrorism.