By Steve Kingstone
BBC correspondent in Washington
The Bush administration has responded coolly to a request from the UN's nuclear agency that its experts be allowed to return to Iraq.
ElBaradei: Deeply concerned
The director of the International Atomic Energy Agency, Mohammed ElBaradei, expressed concern about the looting and destruction of nuclear sites.
He warned that stolen radioactive material can end up in the hands of terrorists.
But the United States insists it is still too early for UN inspectors to return.
On the face of it, the warning from Mr ElBaradei has made little impression on Washington.
A State Department spokesman acknowledged that the United States was in touch with the UN's nuclear agency, but he said now was not the right time for international inspectors to return to Iraq.
The Bush administration argues that until the country is fully stabilised, the task of securing and searching suspected weapons sites is best left to coalition forces.
It says the UN's nuclear inspectors lack the resources to operate in a military environment.
But Mr ElBaradei appears to be accusing the United States of being partially responsible for the lack of security.
"I am deeply concerned by the almost daily reports of
looting and destruction at nuclear sites," he said, in a statement.
Behind the scenes, the US administration is sure to take the warning on board and perhaps look again at the way it patrols these sites.
In the longer term, Washington is leaving open the possibility that the inspectors might return to Iraq.
The latest draft resolution on UN sanctions, sponsored by London and Washington, says the issue of inspections will be revisited, but it doesn't specify when, and for now, the Bush administration is keeping a firm grip on this process.