The U.S. special envoy to the coalition fighting Islamic State (IS) militants says the group's ranks of foreign fighters have dropped to about 25,000 from a peak of 35,000.
Brett McGurk said on February 23 that the extremist group was under pressure and had cut fighters' salaries by about half.
The comments come as an accord between the United States and Russia to scale back violence in Syria is supposed to start on February 27. The truce does not include the IS group and other terrorist organizations.
McGurk also said the IS group was trying to attract as many foreign fighters to Libya as possible, adding that IS activity in the North African country was particularly concerning to the United States.
Libya has been torn by conflict since the 2011 uprising against dictator Muammar Qaddafi.
Armed factions supporting rival governments in Tripoli and Benghazi have battled for power while also fighting against Islamist fighters, including many loyal to the IS group.