WASHINGTON : A US lawmaker said Monday he is blocking $75 million in aid to war-torn Afghanistan until President Barack Obama’s administration provides information on alleged “secret cash payments” to President Hamid Karzai.

Senator Bob Corker, the ranking Republican on the Senate Foreign Relations Committee, has written a fourth letter to the Obama administration complaining about the policy.

“The administration’s lack of any response to these requests, its apparent decision to flout the Foreign Relations Committee’s oversight, and its inability (or unwillingness) to explain such a policy is unacceptable,” Corker wrote in a Monday letter to John Kerry and US Agency for International Development chief Rajiv Shah.

“As a consequence, I have determined that the further commitment of taxpayer funds at this time toward such an incoherent governance strategy would not be in our national interest, and I am placing a formal hold on Congressional Notification 65, relating to USAID programmes in Afghanistan.”

Karzai acknowledged in April that his office received money delivered by the Central Intelligence Agency, as first reported by The New York Times which said the secret funds amounted to tens of millions of dollars over the last decade.

But he later denied that the CIA cash was used to buy the support of warlords who could tip the country back into civil war, saying it instead was used to pay wages for government employees, as well as health care and scholarships.

Warlords who fought against both the Soviet occupation in the 1980s and Taliban regime retain huge influence, and many have close links to Karzai’s government that came to power after the Taliban were ousted in 2001.

With the NATO-led mission winding down after more than 11 years of fighting, the warlords look set to renew their battle for power in Afghanistan and the weak central government faces a tough challenge to impose stability.

Corker said the blocked funding was intended for electoral programmes in Afghanistan, and that the hold “will remain in place until such time as I receive sufficient information on these matters.”