Nato's secretary general says it was "unfortunate" that western officials were forced out of Afghanistan for allegedly talking to the Taleban.
Taleban militants continue to battle Nato forces in Afghanistan
Two diplomats from the UN and the EU left the country on Thursday because the Afghan government said they posed a threat to national security.
Jaap de Hoop Scheffer said a political process was vital to resolving the situation in Afghanistan.
One of the pair was a high-ranking British UN employee, Mervyn Patterson.
Mr de Hoop Scheffer told BBC Radio 4's Today programme that the effort in Afghanistan was not just about the military.
"Afghanistan, and Nato's operation in Afghanistan, is not about military victory.
"It is about rebuilding the nation, it's about development, it's about reconstruction, and it's also very much about a political process.
"I think any form of political process should be supported - short of, of course, talking to people who behead people, who burn down schools, who commit the most serious atrocities we have seen recently."
The other expelled diplomat was the acting head of the EU mission in Afghanistan, Irishman Michael Semple.
The Kabul-based pair were accused of posing a threat to national security during a visit to Helmand province.
There has been no official explanation as to exactly why the men were told to leave.
The United Nations has argued that the expulsions are a result of a misunderstanding.
However, the governor of Helmand province, Asadullah Wafa, said he had warned the diplomats not to meet the Taleban who are "fighting us and training suicide bombers".