Afghan National Army soldiers load their belt-fed machine gun during a mock attack on an enemy's stronghold during a military training exercise at Kabul Military Training Center, in Kabul, Afghanistan, Oct. 22, 2014.

If you're curious what America is getting for its multi-billion dollar effort to train and equip local security forces in Afghanistan, sorry, that's now classified.

In its most recent quarterly report to Congress, the Special Inspector General for Afghanistan Reconstruction (SIGAR) sharply criticized a new move by the U.S.-led International Security Assistance Force (ISAF) to classify even the executive summary of its regular reports on the capabilities of the Afghan forces in which the U.S. has invested more than $61 billion.

The regular ISAF reports, most recently called the Regional ANSF Status Report (RASR), have been produced by ISAF in some form since 2008. A majority of the contents always have been classified, since they deal with ground-level capabilities of Afghan forces - potentially useful intelligence for insurgents - but the executive summary was not. SIGAR called the sudden, "inexplicable" classification "deeply troubl[ing]" and a direct hit to government accountability.

"ISAF's classification of the report summary deprives the American people of an essential tool to measure the success or failure of the single most costly feature of the Afghanistan reconstruction effort," SIGAR said in its latest quarterly report to Congress. "SIGAR and Congress can of course request classified briefings on this information, but its inexplicable classification now and its disappearance from public view does a disservice to the interest of informed national discussion."

"It is not clear what security purpose is served by denying the American public even high-level information," the SIGAR report says.

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Lt. Col. Chris Belcher, a public affairs officer at ISAF in Afghanistan, told ABC News in an email that the move was made to "address potential concerns about operational security" after a reevaluation in August.

"After careful review, it was determined that the entirety of the report was classified to include the executive summary which contained Afghan-provided readiness information," Belcher said. "While we appreciate and understand SIGAR's responsibility to provide information to Congress and the American public, we have a responsibility to protect data that could jeopardize the operational security of our Afghan partners to include unnecessarily highlighting possible vulnerabilities and capability gaps; information which could provide adversaries critical intelligence that could be exploited, endangering the lives of our Afghan partners and coalition forces serving alongside them."

READ: SIGAR Report to Congress