The Pentagon attracted renewed criticism on Friday, from a government watchdog, for the purchase of Russian-made helicopters and other aircraft for an Afghan Special Forces unit, which it said did not have enough troops or expertise to operate the equipment.

The Special Inspector General for Afghanistan Reconstruction, or SIGAR, a U.S. supervisory body, which oversees funds worth almost $90 billion for reconstruction programs in the troubled country, said the Pentagon awarded a $553.8 million contract to Russian arms dealer, Rosoboronexport, for 30 Mi-17 helicopters, ignoring recommendations to suspend the plan to avoid wastage.

“We are disappointed by this decision and continue to question the wisdom of this contract action,” SIGAR said in a report released Friday. “Without an effective support structure, U.S.-funded SMW aircraft could be left sitting on runways in Afghanistan, rather than supporting critical missions, resulting in waste of U.S. funds.”

SIGAR said the Pentagon also awarded a $218 million contract to a U.S. firm, Sierra Nevada Corporation, to buy 18 PC-12 fixed-wing aircraft, for Afghan Special Mission Wing, or SMW, which was established to support counterterrorism and counternarcotics operations. As of January, the SMW had only 180 personnel, or less than one-quarter of the personnel needed to meet operational capacity.

Friday’s report on the Rosoboronexport contract is expected to stir further criticism against the Pentagon, which is already under fire for doing business with Russia’s state-run arms exporter that also supplies weapons to Syrian President Bashar al-Assad.

The Department of Defense's announcement, on June 17, about the purchase of the 30 Russian-built choppers, came days after U.S. lawmakers approved a defense policy bill for 2014, which upheld a ban on contracts with Rosoboronexport.

The report disputed the Pentagon’s argument that delaying the acquisition and delivery of the equipment would also delay efforts to improve SMW’s capabilities. Instead, the report said, the delays in recruiting and training of SMW personnel, who are Afghan locals trained by U.S. forces, were mainly due to tensions between the Afghan interior and defense ministries.

The report urged the Pentagon to suspend the contracts until an agreement on recruitment of SMW personnel was reached between the Afghan ministries.

The Pentagon began purchasing helicopters for Afghan forces from Rosoboronexport in May 2011, and, including this month’s contract, has spent more than $1 billion on Rosoboronexport helicopters and maintenance services, according to Reuters.

The ban on buying equipment from Rosoboronexport came into effect in the 2013 National Defense Authorization Act, but Pentagon officials maintain that they have not broken the rules, as funding earmarked for 2012 was used to pay for this month’s contract, Reuters reported.