NATO leaders are in Chicago for a summit to discuss how to achieve an orderly withdrawal from Afghanistan.
Afghan President Hamid Karzai and his Pakistani counterpart Asif Ali Zardari are there with heads of state and government from the 28 NATO countries.
The BBC reports several NATO leaders are under domestic pressure to withdraw troops from Afghanistan before 2014.
New French President Francois Hollande has promised to pull out the country's forces by the end of this year.
However, NATO Secretary General Anders Fogh Rasmussen said such moves were part of the plan.
''We are now in a process of gradually handing over lead responsibility for security to the Afghans and that process will be completed by the end of 2014 and during that process you will see withdrawal of troops, a shift from combat to support,'' he told the BBC.
''It's not a contradiction of our strategy, it's a part of our strategy,'' Mr Rasmussen added.
Earlier in May, the Taliban announced the start of their annual spring offensive. On Saturday a suicide bomber killed at least 10 people at a checkpoint in the eastern province of Khost.