Mr Holbrooke's trip coincided with the killing of a provincial politician
US special envoy Richard Holbrooke has travelled to north-west Pakistan to see at first hand the troubles caused by the militant insurgency.
As the envoy for Afghanistan and Pakistan arrived in Peshawar, a bomb attack left a local politician dead.
Mr Holbrooke was given a briefing by top officials on deteriorating security in North West Frontier Province.
The envoy is on a regional visit expected to also take in Afghanistan and India.
The politician who was killed - Alamzeb Khan, a member of the provincial parliament and a leader of the ruling ANP party - died when a roadside bomb destroyed his car as he was leaving his home in Peshawar.
There appeared to be no threat to Mr Holbrooke.
'Listen and learn'
The special representative met senior politicians and tribal leaders and also visited the Khyber tribal region close to Peshawar.
The area has been the scene of a number of attacks on convoys carrying supplies to US and Nato troops in Afghanistan.
The BBC's Syed Shoaib Hasan in Islamabad says Mr Holbrooke is being seen as a key actor in a new effort to reverse the deteriorating situation on both sides of the Pakistan-Afghanistan border.
Mr Holbrooke had earlier met Pakistan's political leadership, including President Asif Zardari, Prime Minister Yusuf Raza Gilani and Foreign Minister Shah Mehmood Qureshi.
He also held meetings with Gen Ashfaq Pervez Kayani, the country's army chief, and Lt Gen Ahmad Shuja Pasha, director-general of the ISI intelligence agency.
Mr Holbrooke has said he is in the region to "listen and learn" and will report back to President Barack Obama and Secretary of State Hillary Clinton.
Before his trip the envoy called the situation in Pakistan "dire".
The US and Pakistan have had serious disagreements over the Afghan border zone, with Washington unhappy at Pakistani efforts to tackle militants and Islamabad condemning US drone attacks inside its territory.
On Tuesday, Mr Gilani said his country and the US must base their relationship on "trust, cohesion and understanding".