David Cameron and Afghanistan's President Hamid Karzai are to discuss what support is needed from the international community after troops withdraw from the country in 2014.
It comes as France said it plans to pull out most of its military personnel by the end of 2013 - a year earlier than the Nato deadline.
French President Nicolas Sarkozy made the announcement following talks with his Afghan counterpart.
At the Prime Minister's country residence Chequers, Mr Cameron and Mr Karzai will discuss security progress and will sign a pledge setting out the next stage in relations between Britain and Afghanistan.
The "enduring strategic partnership" renews a 2005 agreement and sets out a shared vision of a secure, stable and prosperous Afghanistan able to maintain its own security and stop international terrorists using it as a safe haven, officials said.
It also ensures the UK is supporting the development of Afghanistan at the grassroots level with concrete action that directly benefits civilians, according to Downing Street.
Some of that work is already under way, including the creation of new police stations, education schemes for women and a UK-funded Afghanistan Business Innovation Fund.
British troops are to end their combat role at the end of 2014.
Asked about troop withdrawals during a pre-Christmas visit to soldiers serving in Afghanistan, Mr Cameron said: "I don't want to see some massive cliff-edge in 2014 - I don't think that's practical.
"But I don't think we need to make hard and fast decisions at this stage."
He said there was "an ongoing conversation with our allies" about how and when Nato forces would be withdrawn over the next three years.
"I'm absolutely clear that the British public deserve to know there is an endpoint to our involvement in Afghanistan and that endpoint is 2014."
Today's meeting follows the last-minute cancellation of talks in December after a series of bombings in Afghanistan in the first serious resurgence of sectarian violence in a decade.
:: A British soldier has died after suffering a gunshot wound while on patrol in Helmand Province, Afghanistan, the Ministry of Defence has said.
The 1st Battalion The Yorkshire Regiment soldier was serving as a member of an International Security Assistance Force foot patrol to disrupt insurgent activity when he came under attack.
His family have been informed of his death.