Washington CNN  — 

President Donald Trump acknowledged the possibility that ISIS and other terror groups could regain their strength in Syria and Afghanistan if he withdraws or reduces troops in those countries and noted that he would send US forces back if they did.

Trump, who announced in December that he was ordering staff to execute a “full” and “rapid” withdrawal of US troops from Syria, made the comments in an interview taped Friday with CBS’s Margaret Brennan on “Face the Nation.”

“Because the concern in here by your intelligence chiefs, though, is that you could in that vacuum see a resurgence of ISIS,” Brennan said.

“Sure,” Trump replied.

“See a resurgence of terror groups like Al-Qaeda,” Brennan continued.

“And you know what we’ll do? We’ll come back if we have to,” Trump said.

“We have very fast airplanes, we have very good cargo planes. We can come back very quickly, and I’m not leaving,” he said. “We have a base in Iraq and the base is a fantastic edifice. I mean, I was there recently, and I couldn’t believe the money that was spent on these massive runways. And these – I’ve rarely seen anything like it.”

On Friday, CNN reported that the Pentagon believes that ISIS could re-emerge and take back territory in Syria within months if the US does not maintain military pressure on the terror group, according to an official familiar with the latest assessment. Another US official said that some military and intelligence officials are concerned it could happen even sooner.

The President noted the military is still fighting ISIS from its base in Iraq, adding that some of the troops in Syria will be shifted to Iraq.

“They’re starting to, as we gain the remainder, the final remainder of the caliphate of the area, they’ll be going to our base in Iraq, and ultimately some will be coming home,” Trump said when asked when the troops in Syria would be returning.

During his 2016 presidential campaign, Trump attacked former President Barack Obama for his decision to draw down troops in Iraq, dubbing his predecessor “the founder of ISIS” because, he argued, the Islamic State flourished in the vacuum left by American forces.

CNN’s Barbara Starr contributed to this report.