Pakistan's Foreign Minister Shah Mahmoud Qureshi has promised that the country's resolve would not be shaken shaken after a huge car bombing he described as a heinous crime.
It killed at least 105 people in a busy market in Peshawar, in northern Pakistan, with almost 200 more wounded.
At least 60 of the dead were women and children.
The bombing was the deadliest attack in Pakistan this year.
It came as US Secretary of State Hillary Clinton began a visit to the Pakistani capital, Islamabad.
Mrs Clinton, who was at a news conference with Mr Qureshi, says the United States is "standing shoulder to shoulder" with Pakistan in its fight against "brutal extremist groups".
She endorsed the call for an end to the killing of innocent people in the country, saying the Obama administration wanted a relationship with Pakistan that goes beyond co-operation against terrorism.
The BBC says the Taliban have denied being behind this bombing, but the government blames them for a wave of attacks apparently launched in response to the army operation against their strongholds on the Afghan border.
The BBC correspondent in Islamabad says that few people will take the Taliban's denial seriously and they remain the major suspects for the bombing, if only because few other groups would have a motive for carrying out such a devastating attack.