The Pakistani government accused the US of sabotaging peace talks with domestic Taliban fighters by killing their leader in a drone strike.
The rise in tension, even though the US took out Pakistan’s No 1 enemy, shows just how complicated the relationship between the professed allies can be.
The two have repeatedly clashed over issues such as drone strikes and Pakistan’s alleged support for militants fighting US troops in neighbouring Afghanistan.
The Pakistani Taliban leader killed on Friday, Hakimullah Mehsud, was a ruthless figure known for a deadly attack on a CIA base in Afghanistan and a bloody campaign that killed thousands of Pakistani civilians.
Pakistan’s government, which took office in June, has pushed peace talks with the Taliban as the best way to end the conflict, although many are sceptical a deal is possible.