"We don't think it's needed at this time," a senior state department official said in Washington on condition of anonymity.
"The inspectors' purpose was to ensure compliance with the UN Security Council resolutions, and those resolutions are sort of overtaken by events,” the official said on Tuesday.
“There might be a role for UN inspectors at some point in the future, but that debate is way down the road," the official added.
The official's comments were in response to remarks on Sunday by International Atomic Energy Agency (IAEA) head Muhammad al-Baradai, who said UN inspectors should be allowed to return as quickly as possible to "finish the job".
All the information made public up to now "supports our tentative conclusion before the war that we haven't seen any evidence that Iraq was trying to reconstitute its nuclear weapons programme," al-Baradai said.
"I think it would be prudent for us to go back to Iraq and, frankly, finish the job."
Earlier, two leading UN officials in Iraq were relieved of their duties pending an inquiry into security lapses exposed after August's deadly Baghdad bombing.
Ramiro Lopes da Silva, who was heading the UN mission in Iraq since the killing of Sergio Vieira de Mello in August, and UN Security Coordinator Tun Myat have gone on leave until mid-January.
Da Silva, the acting chief of the
UN in Iraq, is on leave
Both men reportedly volunteered to step aside while the review over perceived security lapses facilitating the bombing of the UN compound in Baghdad is carried out. The attack killed more than 20 people and left at least 150 wounded.
"Accordingly, the secretary-general has decided that they will take special leave until mid-January, while remaining available to the team to provide relevant information," UN spokesman Stephane Dujarric said.
The announcement came amid growing pressure on UN Secretary-General Kofi Annan to take action for the "security lapses".
An independent probe has already indicted the UN security network in Iraq as "sloppy" and "dysfunctional".
De Mello was among 22 people killed when a huge truck-bomb explosion ripped through the main UN compound in Baghdad on 19 August.
The blast also forced international aid agencies to reassess their presence in Iraq. The UN has temporarily pulled out its international staff from the country because of security concerns.