David Cameron is to hold talks later with Afghanistan's president Hamid Karzai and the prime minister of Pakistan.
It marks the first time Pakistani Prime Minister Raja Ashraf has visited Afghanistan since being elected last month.
Downing Street sources said Mr Cameron is keen to point out that having a safe and secure Afghanistan is in both countries' interests, and they should work together, along with support from the international community to try to achieve this.
The meeting in the capital Kabul follows the Prime Minister's visit on Wednesday to British troops in Helmand Province.
Discussions are expected to focus on the security situation in the country and on plans to hand over control to Afghan police and army by 2014.
It is thought the Prime Minister will set out further details of plans to establish a British-run officer academy in the country, with the aim of creating a facility similar to that of Sandhurst in the UK.
A Downing Street spokesman said Mr Cameron was keen to reinforce the message to the Afghan government that they would continue to receive support in terms of development and security after the planned 2014 withdrawal.
However, Afghan national forces will be expected to meet their own responsibilities.
Earlier this month, at a meeting in Tokyo, the international community made commitments to long-term development aid.
This will be Mr Cameron's first visit to Kabul in a year, although he held important meetings with President Karzai at the Nato summit in Chicago in May and at Chequers in January.
Mr Cameron told reporters on Wednesday that plans would be set out in the autumn to withdraw a significant number of troops next year, ahead of the 2014 deadline for full withdrawal.
However, some senior military figures at the UK forces HQ at Camp Bastion expressed their concern at the capability of Afghan forces to maintain stability unless International Security Assistance Force (Isaf) troop numbers remain high for at least the next two years.
