A top Obama administration official says the Islamic State group's ranks of foreign fighters have dropped to about 25,000 from a peak of 35,000, the Associated Press reports.

Brett McGurk is the U.S. special envoy for the global coalition to counter IS. He says fighters from 120 countries have joined IS.

McGurk is touting progress in the U.S.-led effort to defeat IS. He says the extremist group is under pressure and has cut fighters' salaries by about half.

McGurk says President Barack Obama will get an update on diplomatic and political efforts Thursday, February 25, at the State Department.

The meeting comes after the U.S. and Russia announced a ceasefire agreement for Syria to take effect later this week. McGurk says the U.S. is under no illusions about how difficult implementing the ceasefire will be.