The US military says it is expanding several Iraqi prisons, including Abu Ghraib jail in Baghdad, to cope with a sharp rise in detainees.
Abu Ghraib became notorious for prisoner abuse last year. It was due to be shut down but now it is nearly full.
The $50m construction programme will allow the US to hold 16,000 prisoners in Iraq, up from 10,000 currently.
The announcement comes a day after US Defence Secretary Donald Rumsfeld warned the insurgency could last years.
Scandal
US military spokesman Lieutenant Guy Rudisill said the expansion plan was a result of "successful military operations against the insurgency and terrorists by coalition forces and the Iraqi special forces".
Abu Ghraib prison, which currently holds 3,537 Iraqi and Arab detainees, is expected to have room for another 800 inmates by the end of July.
Camp Cropper, near Baghdad airport, which has 125 high-profile prisoners, will be expanded to contain an extra 2,000.
Camp Bucca, in the southern port city of Umm Qasr, currently holding 6,340 detainees, will see its capacity increased by 1,400 places.
A fourth prison is to be built from scratch in Sulaimaniya, 330km (205 miles) north of Baghdad.
The US-run camps are for "security detainees" held by coalition forces as suspected insurgents. Iraqi prisoners not connected to the insurgency are held in regular Iraqi jails.
Allegations of abuse by US soldiers at Abu Ghraib emerged in April 2004 and dealt a serious blow to the coalition's efforts to win over Iraqi hearts and minds.
The scandal drew international condemnation and several soldiers have since been convicted of offences relating to the abuses.
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