Nawaz Sharif was speaking at a joint press conference with President Ashraf Ghani after their talks in Islamabad.
The two sides reviewed the entire gamut of bilateral relations with focus on expanding cooperation in the areas of trade, investment, energy and building infrastructure, the leaders said.
"I reaffirmed Pakistan's support for the intra-Afghan reconciliation process that the new government is initiating. This process, we agreed, must be fully Afghan-led and Afghan-owned," Xinhua quoted the Pakistani prime minister as saying.
"I underlined Pakistan's commitment to comprehensively upgrade cooperation in all fields -- including border security and defence, Afghanistan's reconstruction and rehabilitation, capacity building, parliamentary exchanges, and cultural, educational and sports links," Nawaz Sharif said.
President Ghani, who arrived in Islamabad Friday on a two-day state visit, called for the beginning of a new era of mutual trust and cooperation in all areas between the two countries.
"We are going to leave past behind and work for the future of Pakistan and Afghanistan. We are going to have renewed attentions," Ghani said.
The Afghan president also invited Prime Minister Nawaz Sharif to visit his country.
Pakistan is one of the first countries President Ghani, who was sworn in in September, has chosen to visit.
He earlier toured Saudi Arabia and China.