Anonymous sources with insider knowledge on the ongoing peace negotiations between the US government and the Taliban say that the talks almost broke down various times and progress is slow due to various fundamental disagreements, including how terrorism may be defined.

The question about what defines terrorism is a crucial part of the negotiations as it could determine what will and what won’t qualify as a violation of a potential peace agreement. This is because the US and the Taliban have broadly agreed that such an agreement would result in a withdrawal of US forces from Afghanistan under condition that the country will not be used by militant groups to launch attacks against the US and allied countries. However, while the US wants the agreement to specifically mention “terrorist” groups, the Taliban has so far refused to accept this explicit reference to terrorism because the terms lacks a universal definition.

Read more: U.S. Peace Talks With Taliban Trip Over a Big Question: What Is Terrorism?