Story highlights The funds are used to reimburse Pakistan for the cost of military operations

This is the second time these funds have been withheld from Islamabad

(CNN) Secretary of Defense James Mattis has informed Congress that the US is withholding $50 million in funding from Pakistan because he was unable to certify that Islamabad "has taken sufficient action against the Haqqani Network," a branch of the Afghan Taliban.

Such certification is necessary in order to enable Pakistan to receive reimbursement of "Coalition Support Funds" for 2016. The funds are used to reimburse Pakistan for the cost of military operations against terrorist groups during 2016.

There was about $50 million remaining in the funds, which will now be repurposed the Pentagon said.

"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 (NDAA)," Pentagon spokesman Adam Stump told CNN in a statement.

While many analysts believe that a tougher line on Pakistan for its connections to the Haqqani Network will be part of the administration's new strategy for Afghanistan and the wider region, the Pentagon said that Friday's announcement was unrelated to the wider review.

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