The occupation troops’ deputy director of operations, Brigadier General Mark Kimmitt, had described the captive Sayed Amir Yassari as "operations director in Sadr City of Moqtada Sadr".
But in the face of strong denials from a Sadr spokesman that Yassari had any current position in his organisation, another US spokesman on Thursday backtracked on the accusations against the cleric, who has substantial support.
The report of a link between Yassari and Sadr was "speculation" based on "gossip from the street", said Captain Sean Kirley, spokesman for the 2nd Armoured Cavalry Regiment, which patrols the area.
Earlier, aides of Moqtada Sadr, who runs the anti-US Mehdi Army militia, denied any connection with the US detainee, suspected of being behind attacks on US soldiers and Iraqi civilians in the capital.
Sadr's Mehdi Army has had a stormy relationship with the US military.
Meanwhile, resistance fighters attacked a police station in western Iraq and a mine blew up a US military vehicle in Baghdad on Thursday.
Three civilians and two policemen were wounded in the attack on the police station in the heart of the western town of Ramadi.
US unable to control resistance
Attackers fired small arms and rocket-propelled grenades from a black BMW in the assault in Ramadi.
"One police major, Muhammad Ibrahim, was wounded in the leg and one policeman called Mohannad Sallun is seriously hurt and has been transferred to Baghdad," deputy police chief Lieutenant Samir Habib Jalil said.
"Four grenades were thrown and shots fired from automatic weapons against the station and police riposted," said witness Luai Abdul Karim.
In the capital, smoke was seen pouring out of a field artillery ammunition support vehicle after it hit a landmine at a major motorway intersection.
"The vehicle did catch fire but there were no injuries," a US spokesman said.