Pakistani military sources have rejected a US report which says the country may have misused more than $2bn given to it for the "war on terror".
The report by the US Government Accountability Office says there is no adequate proof that Pakistan used the funds for their intended purpose.
A Pakistan army spokesman refused to comment, saying it was a matter for the US Congress and the Pentagon.
The report was compiled by auditors on behalf of the US Congress.
Government Auditing Office (GAO) auditors faulted "Pentagon oversights" between 2004 and 2007 and defence officials had not obtained sufficient documentation from Pakistan to verify that claimed costs were correctly reported.
Sovereign country
The Pentagon responded by saying that the GAO had failed adequately to acknowledge Pakistan's "significant contribution" to fighting terrorism or the "flexibility" required in "contingency environments", the Washington Post reported
US defence officials argued that Pakistan - like other recipients of US funds - is a sovereign country that may not meet US accounting standards.
But a Pakistani army source told the BBC that some US officials are aware of conditions in the combat zone and know why spending procedures cannot always be followed.
Since the September 2001 attacks on the World Trade Centre, the US has disbursed more than $10bn to Pakistan as part of its worldwide counter-terrorism effort.
More than $5.5bn of this money was paid out of the Coalition Support Fund (CSF), meant to fund Pakistan's war effort against al-Qaeda and Taleban.
The GAO report points out several instances where expenses are not backed either by documentation or physical verification.
These include $20m for army road construction and $15m to build bunkers.
The report also points out that an air defence radar system, for which Pakistan sent a bill of $200m to the US, may not have met US requirements.
It also says that monthly payments averaging $19,000 per vehicle for 20 passenger vehicles used by the Pakistani navy may contain "duplicative charges".
But a source in the Pakistan army says much of what has been pointed out in the report does not take into account facts on the ground.
He said that Pakistan's economy is largely undocumented and it is not always possible to follow accurate accounting procedures for every expense incurred.
"How do you document flying hours of helicopters in the war zone, or the wear and tear of equipment?" he asked.
