The U.S. Defense Department has withheld $50 million in Pakistan military payments after Pentagon chief Jim Mattis determined Islamabad is not doing enough to counter the Taliban-affiliated Haqqani network, an official said Friday.

"The funds could not be released to the Government of Pakistan at this time because the secretary could not certify that Pakistan has taken sufficient action against the Haqqani Network per the requirement in the FY 2016 National Defense Authorization Act," Adam Stump, a Pentagon spokesman, said as quoted by Reuters.

This is not the first time the Pentagon has decided not to make military reimbursements. Last year, it withheld $300 million.

"This decision does not prejudge the conclusions of the White House review of South Asia strategy, which is still ongoing," Stump said.

Pakistan has been reimbursed $550 million of the $900 million the country was authorized to receive in fiscal year 2016.

Of the rest, $300 million had already been reprogrammed for other purposes, but had not been previously reported. Mattis' latest decision affects the remaining $50 million.

The Pentagon decision comes as the United States is trying to figure out a strategy to break the stalemate with the Taliban in Afghanistan.

Mattis has indicated he wants the plan to incorporate much of the broader region and not merely focus on Afghanistan.

The Taliban-affiliated Haqqani network is led by Sirajuddin Haqqani.