(National Journal) — The Central Intelligence Agency is continuing to use a covert base inside Pakistan for drone strikes and other counterterrorism operations despite Islamabad’s public insistence that the facility has been closed, highlighting the increasingly complicated relationship between the two nominal allies in the wake of Osama bin Laden’s killing there earlier this year.

Senior U.S. and Pakistani officials said in interviews on Friday that CIA operations at the Shamsi air base in western Pakistan, a short distance from the Afghan border, were continuing unabated and that no American personnel had been withdrawn from the facility. The base is the hub of the CIA’s escalating campaign of drone strikes against militant leaders throughout Pakistan, a push that Obama administration officials credit with decimating the leadership of al-Qaida and many of its Islamist allies.

“It’s business as usual,” a U.S. official familiar with the matter said. “There have been no operational changes there.”

The comments contradicted earlier remarks from Pakistani Defense Minister Chaudhry Ahmed Mukhtar, who told The Financial Times in an interview published on Friday that Islamabad had forced the CIA to stop using Shamsi for drone strikes and to withdraw its personnel from the facility. . . .

American officials, for their part, have made clear that they have no plans to wind down the drone campaign against militant targets inside Pakistan. Unmanned CIA Predator drones carried out at least 12 strikes inside Pakistan in June, the highest monthly total of the year, according to Long War Journal, a Web site tracking the campaign. So far this year, the CIA has carried out at least 40 such strikes, killing an estimated 269 militants, according to the site. Last year, the U.S. carried out a record 117 drone strikes inside Pakistan, double the 2009 level.