Saturday's massive truck bombing, which killed at least 50 people, is seen as a warning to the Pakistani government over its cooperation with the US.
US forces may have sent in ground troops for the first time Wednesday. Were they targeting a top Taliban or Al Qaeda figure?
The heightened political tensions between the two allies in the war on terror has prompted US presidential hopefuls to focus on improving Afghanistan strategy.
They seem to be moving from Iraq to Pakistan and Afghanistan.
Tuesday's deadly US incursion is under investigation, but it points up the contrast between the two nations' approaches to militants along the Afghanistan border.
Wednesday, a US airstrike killed 11 Pakistani soldiers near the Afghan border.
Tehrik-e-Taliban carried out Sunday's bombing, the deadliest since the new Pakistani government took power in March. The suicide attack came two days after the militants freed the Pakistani ambassador to Afghanistan, Tariq Azizuddin.
The US is increasingly out of sync with Pakistan's newly-elected government, say analysts.
The Awami National Party, which leads the ruling coalition in the crucial North West Frontier Province, espouses a nonviolent approach to tackling extremism.