Between 500 and 600 U.S. troops are expected to remain in Syria when all is said and done, Chairman of the Joint Chiefs of Staff Army Gen. Mark Milley said on Sunday.

Milley's comments on ABC News' “This Week” indicate the U.S. military's footprint in Syria will end up being roughly half the size it was before Turkey invaded Kurdish-held northeast Syria last month.

“There will be less than 1,000 ; for sure, and probably in the 500-ish frame – maybe 600 – but it's in that area,” Milley told Martha Raddatz during an interview. “But we're not going to go into specific numbers because we're still going through the analysis right now.”

Defense Secretary Mark Esper initially announced on Oct. 13 that most U.S. troops would leave Syria after the Turkish military and their Arab proxies pushed further into Kurdish territory than initially expected. But after President Donald Trump announced that the United States would secure Syrian oil fields, the U.S. military dispatched Bradley fighting vehicles around Deir ez-Zor – the site of a 2018 battle between Russian mercenaries and U.S. forces.

Despite the president's repeated comments about the need to protect Syrian oil fields, Pentagon officials insist the reason why U.S. troops are staying in Syria is to continue fighting ISIS.

Milley did not discuss securing the oil fields during his interview on Sunday.

“There are still ISIS fighters in the region and unless pressure is maintained, unless the tension is maintained on the group, then there's a very real possibility the conditions could be set for a reemergence of ISIS,” Milley told Raddatz.

“We are committed to doing that,” he continued. “The footprint will be small but the objective will remain the same: The enduring defeat of ISIS.”