The 2nd Brigade Combat Team, 82nd Airborne Division, was part of the extra 30,000 soldiers sent last year.
"I can state that (they) are leaving and there is no replacement brigade combat team coming in," U.S. military spokesman Lieutenant-Colonel Steve Stover told Reuters.
30,000 troops became fully deployed in mid-2007.
There are more than 150,000 U.S. troops in Iraq, with about 34,500 deployed in the Iraqi capital. The drawdown is expected to cut the overall total by about 20,000.
Last November, the first brigade, totalling about 3,000 soldiers, was sent home from Iraq without being replaced.
Stover said the 2,000 soldiers of the 2nd Brigade Combat Team based in northeast Baghdad were also in the process of returning home after a 15-month tour. They included support and service staff as well as combat troops.
For operational reasons he could not say whether other U.S. soldiers or Iraqi forces would fill the gap left by the departing brigade.
But there were plans to withdraw another brigade from the Baghdad area as part of the planned cutback, he said, giving no details of when that would take place.
Petraeus and U.S. Defense Secretary Robert Gates have said there should be a pause after the planned drawdown is completed in mid-2008 to assess the situation. That would leave about 140,000 U.S. soldiers in Iraq.
Güncelleme Tarihi: 07 Mart 2008, 11:26