Defense Secretary Robert Gates on Saturday suggested US lawmakers are kept fully informed about CIA operations abroad, including widely reported drone bombing raids on militants in Pakistan.
Asked about CIA accountability in conducting air strikes in Pakistan, Gates avoided openly acknowledging the raids, saying he could not "get into discussion of any kind of operations".
But Gates, a former director of the spy agency, insisted the Central Intelligence Agency and the US military was fully accountable to Congress in all its operations.
"I have no doubt whatsoever that the intelligence committees in the United States Congress are fully informed of the activities the CIA is carrying out," he said at the Shangri-La security conference in Singapore.
He spoke days after a UN human rights expert urged the United States to sideline the CIA from targeted killings using drones, warning that the practice amounted to "a licence to kill without accountability".
In a report to the UN Human Rights Council, Philip Alston, the special rapporteur on extrajudicial executions, warned that the "prolific" use of targeted killings, mainly by unmanned US aircraft, was setting a damaging example that other countries would follow.
The US State Department has argued that targeted killings abroad are legally justified, citing the principle of self-defence under international law.