David Cameron's plan to withdraw from Afghanistan within five years could encourage Taliban forces to step-up attacks on Western forces, the head of Nato has warned.
Anders Fogh Rasmussen - who was in London for talks with Mr Cameron and Defence Secretary Liam Fox - said there could be no guaranteed withdrawal date for the international troops.
Last month Mr Cameron said he hoped to bring home British troops before the expected date of the next general election in 2015.
Mr Rasmussen, the Nato secretary-general, said that while he understood the desire of elected leaders to bring back their forces, the mission had to continue until the Afghans could take responsibility for their own security.
'We can have our hopes, we can have our expectations, but I cannot give any guarantee as far as an exact date or year is concerned,' he told The Daily Telegraph.
'The Taliban follow the political debate in troop-contributing countries closely.
'If they discover that through their attacks, they can weaken the support for our presence in Afghanistan, they will just be encouraged to step up their attacks on foreign troops.'
Mr Rasmussen, a former Danish prime minister, said that withdrawing too soon from Afghanistan would lead to a renewed terrorist threat from Al Qaeda, and would risk destabilising neighbouring Pakistan.
'The Taliban would return to Afghanistan and Afghanistan would once again become a safe haven for terrorist groups who would use it as a launch pad for terrorist attacks on North America and Europe,' he said.
Following Mr Rasmussen's meeting with Mr Cameron, Downing Street said they had agreed on the 'central importance' of the ongoing international mission in Afghanistan 'to the national security of the UK and all Nato allies'.
'The Prime Minister made clear that success in Afghanistan was his Government's highest foreign policy and national security priority,' a No 10 statement said.
