The agreement will involve deploying 6,000 more troops in the south of the country, a third of them expected to be British.
Thursday’s agreement is set to make Nato’s Afghanistan mission its biggest ever operation outside Europe.
The south and east have been the scene of intense violence which has this year left more than 1,400 dead, making it the deadliest year since 2001.
The agreement provides for a new British-led Nato headquarters in Kabul.
