Key talks on the Afghan peace process involving the leaders of Pakistan and Afghanistan are due to start at the country retreat of UK PM David Cameron.
The talks at Chequers will focus on cross-border security and how to engage the Taliban in effective peace talks.
It will be the third round of discussions since Mr Cameron instigated the trilateral process last year.
Foreign ministers, military leaders and intelligence chiefs will attend the talks for the first time.
Nato troops are scheduled to withdraw from Afghanistan by the end of 2014.
Mr Cameron hosted a dinner with Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari at Chequers, north of London, on Sunday evening.
In-depth talks with both presidents and their key officials get under way on Monday.
UK Foreign Secretary William Hague said the goal was to help the two nations "build closer co-operation around their common interest in a secure future".
As part of the process, Mr Karzai and Mr Zardari have agreed to work together on a framework of co-operation following the international troops' departure next year.
With the Nato withdrawal looming, Afghan President Hamid Karzai has told the BBC he does not want a repeat of the mistakes made when Russia withdrew from Afghanistan a quarter of a century ago, plunging the country into civil war.
Overcoming mistrust
Downing Street said in a statement on Sunday: "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.
"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."
Afghan security forces are expected to control main towns and cities after 2014
Overcoming mistrust between Afghanistan and Pakistan remains a central issue, BBC World Affairs correspondent Mike Wooldridge 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.
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.
