Detainees prepare for prayers at Parwan Detention Center. (Dar Yasin — Associated Press)

Even as U.S.-led forces draw down in Afghanistan, U.S. officials expect the number of detainees at their main prison to increase — and by a significant margin.

Officials had already announced that they would retain control of the Parwan Detention Center north of Kabul well beyond the planned 2012 transfer date because of concerns that the Afghan legal system is still too weak. But U.S. officials recently said they intend to solicit contractors to help expand the facility’s capacity from about 3,500 beds to 5,500 beds.

Parwan, which has been expanded previously, holds about 2,500 detainees. Those detainees include high-profile insurgents as well as Afghans who are suspected of playing more of a peripheral role in the conflict.

The construction project “is part of our established and ongoing transition efforts” with the Afghan government, Capt. Kevin Aandahl, a spokesman for the U.S. task force that oversees detention operations in Afghanistan, said in an e-mail. Aandahl said the expansion was necessary to “accommodate an increase in the number of suspected insurgents being detained as a result of intelligence-based counter- terrorism operations, which we conduct with our Afghan partners.

U.S. control of Parwan has long been a subject of frustration for Afghans, who see it as a symbol of American occupation, and the expansion is unlikely to help matters.

But the alternative for detainee operations in Afghanistan might be worse. The country’s largest Afghan-run prison, Pol-e-Charki — which includes hundreds of suspects detained by U.S. forces — is widely seen as a breeding ground for the insurgency.

The U.S. Army Corps of Engineers’ notice of intent to hire contractors at Parwan, located near Bagram air base, is here.

U.S. officials say they plan to remain in control of the facility until 2014, when all U.S. and NATO combat troops are to be withdrawn.

Staff researcher Julie Tate contributed to this report.