British Prime Minister David Cameron will hold key talks with the leaders of Afghanistan and Pakistan to discuss the Afghan peace process.
The trilateral summit - the third since last summer - is aimed at improving co-operation between both countries to promote regional stability.
For the first time Afghan and Pakistani army and intelligence chiefs will also take part in the discussions.
Nato troops are scheduled to withdraw from Afghanistan by the end of 2014.
In a process initiated by Mr Cameron last year, Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari have agreed to work together on a framework of co-operation following the international troops' departure next year.
The steadily approaching deadline for the military exit will inevitably be a key factor in the talks, not least for Pakistan with its concerns about security across the region from then on, the BBC's World Affairs correspondent, Mike Wooldridge, reports.
Mr Cameron will host a dinner with Mr Karzai and Mr Zardari at his official country residence Chequers north of London on Sunday evening.
He will then hold the in-depth talks with both presidents and their key officials on Monday.
"This trilateral process sends a very clear message to the Taliban: now is the time for everyone to participate in a peaceful political process in Afghanistan," Downing Street said in a statement.
"As the prime minister has set out previously, a stable Afghanistan is not just in the interests of Afghans, but also in the interests of their neighbours and the UK."Overcoming mistrust between Afghanistan and Pakistan remains a central issue, our correspondent reports.
The Afghan government has made it clear that it views the recent freeing by Pakistan of a number of Taliban prisoners as positive, he says.
But it still wants the release of the former second-in-command of the Afghan Taliban, Mullah Baradar, in the hope that a senior figure like him could influence the Taliban to engage in talks with Kabul.
For the first time, the trilateral talks will also include military and intelligence chiefs from both Afghanistan and Pakistan.
Officials believe this could help in tackling some of the most sensitive issues to do with reconciliation efforts, our correspondent says.
Meanwhile Mr Karzai told the BBC's Pashto Service that Afghan people should take the initiative for peace into their own hands.
"As neither the communist government, nor the Mujahedeen brought peace and security to the country, if we do not carefully manage our peace process the way we did not in the past, we will not achieve stability or security," Mr Karzai said.
The first two rounds of the trilateral talks were held in Kabul and New York last year.