Barack Obama, the US president, said last month that his new strategy for success in Afghanistan would include a focus on combating al-Qaeda and Taliban groups who shelter in Pakistan, from where they launch attacks in both nations.
He has made Afghanistan the centrepiece of his foreign policy.
On to Pakistan
After his meetings in Kabul, Holbrooke travelled to Islamabad on Monday.
Mike Mullen, chairman of the US joint chiefs of staff, joined him in the Pakistan capital.
They are due to wrap up their journey with a visit to New Delhi, the Indian capital, on Tuesday.
The tour comes two days after Nato leaders agreed to deploy an additional 3,000 troops to Afghanistan, ahead of presidential elections on August 20.
That is on top of the 17,000 extra troops from the US promised by July and another 4,000 to arrive by September to train Afghan forces.
About 70,000 foreign troops are already in Afghanistan where violence has escalated to its highest level since the US-led overthrow of the Taliban government there in 2001.