The Pentagon said Wednesday that about 11,000 U.S. troops are serving in Afghanistan, not 8,400 as the Defense Department had previously reported.
The higher number emerged following Defense Secretary Jim Mattis's call for a more accurate troop-strength estimate, as the Trump administration worked on a new U.S. policy in Afghanistan.
The chief spokeswoman at the Pentagon, Dana White, told reporters the estimate of 11,000 troops was based on a simplified accounting method that provides greater "transparency" while "increasing commanders' ability to adapt to battlefield conditions."
The lower number of troops cited previously excluded service members on assignment in Afghanistan for less than 120 days — short-term duty that could include temporary combat support or materiel recovery missions.
Lieutenant General Kenneth "Frank" McKenzie Jr., staff director for the Joint Chiefs of Staff, said the new method of counting troops in the field used approximations rather than exact numbers of troops. This, he said, allows commanders "more flexibility" in battlefield deployments.
"We all recognize that whole units are inherently more prepared and more ready than units that are fragmented in order to meet an arbitrary force management level," McKenzie said.
WATCH: U.S. troop numbers on the rise
Fight against IS
White and McKenzie said the changes made in calculating troop strength in Afghanistan would eventually be applied to American troops fighting the Islamic State group in Iraq and Syria.
"We are reviewing Iraq and Syria, and the same guiding principles will govern how we roll out those numbers as well," White said.
The new number of 11,000 does not include any additional troops that Mattis may choose to send to Afghanistan under the new military strategy there. McKenzie said no decision had yet been made on what total troop strength is to be in the weeks and months ahead. Officials have suggested that about 4,000 additional troops will join the fight in Afghanistan.
Mattis had previously acknowledged there were discrepancies between troop strengths listed in war zones and the actual numbers of American forces deployed there. The Pentagon chief told reporters last week that before he sent more troops to Afghanistan he would "level" the number of troops actually there.
In his Aug. 21 speech announcing the new Afghanistan policy, President Donald Trump said giving commanders more flexibility was a primary goal of his new policy, not simply "transparency" about numbers of troops: "We will not talk about numbers of troops or our plans for further military activities. America's enemies must never know our plans or believe they can wait us out."