Washington CNN  — 

More than 25,000 foreign fighters have traveled to Syria, affiliating themselves with various groups to fight or support the conflict there, according to the latest assessment of the Office of the Director of National Intelligence.

That is an increase from May, when the number was 22,500, according to Brian Hale, the spokesman for the intelligence office. The fighters come from over 100 countries.

The assessment provided to CNN is the latest estimate since the most recent one was released in early May.

RELATED: Pentagon may lift ban on transgender people

Of that at least 4,500 are from the West, up from 4,000. The 4,500 includes more than 250 from the U.S., an increase from 180 in their last public assessment. These are people who have a claim on legal residence or citizenship in the U.S. This includes U.S. residents who have traveled or attempted to travel to Syria or Iraq to support the conflicts there. It also includes those currently in the region, as well as those stopped from traveling there, or have returned to the U.S.

The U.S. now estimates more than 20 people from the U.S. have died in Syria after traveling there.

In all cases the numbers are estimates at best, Hale said. It may not always be clear if the changes are due to better intelligence, or if the changes may also be due to more fighters actually coming into the area, and in some cases more being killed.

For example, the new estimates shows ISIS can muster between 20,000 to 30,000 fighters across Iraq and Syria, a slight decline from previous estimates of 22,000 to 32,000. The U.S. also estimates the ISIS ranks now include “hundreds of westerners,” and “a few dozen Americans, up from a dozen or more,” Hale told CNN.