The Central Intelligence Agency (CIA) runs an Afghan paramilitary force that hunts down Qaeda and Taliban militants in covert operations in Pakistan, a US official said Wednesday. Confirming an account in a new book by famed reporter Bob Woodward, the US official told AFP that the Counterterrorism Pursuit Teams were highly effective but did not offer details. "This is one of the best Afghan fighting forces and it's made major contributions to stability and security," said the official, who spoke on condition of anonymity. The 3,000-strong paramilitary army of Afghan soldiers was created and bankrolled by the CIA, designed as an "elite" unit to pursue "highly sensitive covert operations into Pakistan" in the fight against Al-Qaeda and Taliban sanctuaries, according to The Washington Post, which revealed details of the new book. Revelations about a US-run unit operating in Pakistan are sure to complicate Washington's ties with Islamabad as well as Afghanistan's difficult relations with Pakistan. Pakistan's government said it was unaware of any such force and the military flatly denied its existence. "We are not aware of any such force as had been mentioned or reported by the Washington Post," foreign ministry spokesman Abdul Basit told reporters. "But our policy is very clear, we will never allow any foreign boots on our soil... so I can tell you that there is no foreign troops taking part in counter-terrorism operations inside Pakistan." Asked by AFP about the newspaper report, military spokesman Major General Athar Abbas said it was "not true". "No foreign body, no foreign militia, no foreign troops are allowed to operate on our side of the border. Anyone found doing so will be fired upon," he said. US President Barack Obama has sought to pile pressure on militant havens in Pakistan through a stepped up bombing campaign using unmanned aircraft as well as US special forces' operations in Afghan territory. The administration also has pressed Pakistan to go after the Taliban and associated groups in the northwest tribal belt. The US military's presence in Afghanistan and its covert drone strikes in the border tribal belt are subject to sharp criticism and suspicion in Pakistan. Based on interviews with top decision makers, including Obama, Woodward's book describes the US president as struggling to find a way to extricate US troops from the Afghan war amid acrimonious debate among advisers and resistance from the military.