Manning said Wednesday that it took weeks for the Pentagon to release the new official number because military officials wanted to make sure that it was right.
The officials arrived at the number using the same system used to quantify the troops in Afghanistan, Manning said.
The Defense Department on Wednesday acknowledged that the USA has roughly 2,000 troops on the ground in Syria, four times more than what officials had claimed just a month ago. That number is now at closer to 14,000 after the Pentagon sent roughly 3,000 additional US troops to help end the 16-year conflict in Afghanistan.
Figures released by Defense Manpower Data Center in November, which tracks counts of Pentagon military and civilian personnel deployed overseas each quarter, showed almost 2,000 U.S. troops in Syria and more than 9,000 in Iraq. "We are simply revising how we internally conduct force management and publicly report the USA force commitment in Iraq and Syria", said Manning.
The military's "conditions-based" phrase to define troop commitments is in part a reaction to the administration of Barack Obama, which insisted on a calendar-based withdrawal of troops from Afghanistan.
The US defense Department said that soon will provide information about the exact number of American troops stationed overseas, reports Voice of America. Last week, about 400 Marines in an artillery unit - 1st Battalion, 10th Marines - that was carrying out strikes against the Islamic State in the city of Raqqa returned to the United States.
Military officials have long said that despite several high-profile ISIS defeats, military operations against the terror group would continue for some time. That number also is trending downward, he said, as the US -led coalition in both Iraq and Syria transition from supporting offensive combat operations against Islamic State fighters to supporting local security efforts to prevent a reemergence of IS.
The U.S. troops are also focused on training local police forces, ensuring humanitarian aid can flow into areas where it is needed and ensuring local governance where U.S. -backed forces liberated land from ISIS, he said. "Their collective actions call into question their commitment to deal a lasting defeat to ISIS and other extremist groups", the colonel said. With the liberation, fewer USA forces are needed to support Iraqi and Syrian forces kinetically.
"They also do not appear to have a plan for how to bring a meaningful conclusion to the civil war that addresses the fundamental problems that led to the rise of ISIS".
"ISIS left a minefield when they started walking out", he said.
Iraqi, Syrian and coalition forces will continue to capitalize on the momentum generated "and apply continuous pressure on the terrorist networks wherever they operate", Manning said.