Pakistan has pledged to help Afghanistan end a 10-year Taliban insurgency, as the United States prepares to start a gradual troop withdrawal.
Pakistan has maintained close contacts with the Afghan Taliban and is seen as an important player that can push insurgent groups to the negotiating table.
Prime Minister Yusuf Raza Gilani said on Saturday that his country's aim is to support an Afghan-led peace process.
Pakistan has made similar pledges before, but ties between the neighbours have been hampered by mistrust.
The BBC reports Mr Karzai travelled to Pakistan at the personal invitation of President Asif Ali Zardari.
A joint peace commission involving officials from both Afghanistan and Pakistan was also scheduled to meet.
