Islamic State fighters in Iraq and Syria number around 20,000 to 31,500 — a figure far higher than previously estimated, the Central Intelligence Agency has said.
The new calculation includes some 15,000 foreign fighters in Syria alone, including 2,000 Westerners, a U.S. intelligence official told the AFP news agency on Thursday.
The new calculation was made public on Thursday, a day after President Barack Obama pledged to expand an offensive against the extremist group. The plan foresees expanded attacks in Iraq and new support for Iraqi government forces alongside potential airstrikes against Islamic State (IS) targets in Syria.
"CIA assesses the Islamic State of Iraq and the Levant (an alternative name for the group) can muster between 20,000 and 31,500 fighters across Iraq and Syria, based on a new review of all-source intelligence reports from May to August," Ryan Trapani, CIA spokesman, said in a statement. The number is much higher than a previous estimate of 10,000.
Trapani added: "This new total reflects an increase in members because of stronger recruitment since June following battlefield successes and the declaration of a caliphate, greater battlefield activity, and additional intelligence."
Senior U.S. officials have voiced concern at the presence of foreign fighters among the group who hold Western passports, potentially enabling them to return from the battlefield prepared to carry out attacks in Europe or the U.S.
The Islamic State group has taken control of large parts of Iraq and Syria. The group's brutal campaign has included beheadings of rivals and killings of hundreds of members of Iraq's minorities.
In recent weeks, the Islamic State has released videos depicting the beheading of two American journalists in Syria.
The violent images appear to have had an impact on a formerly war-weary public in the U.S., with multiple polls in recent days showing that the majority of Americans support airstrikes in both Iraq and Syria.