Washington (CNN) The commander of US Central Command, which oversees military operations in the Middle East, said Tuesday he "was not consulted" prior to President Donald Trump's December announcement that the US would withdraw its troops from Syria.

And despite Trump's claims that ISIS has been defeated, Gen. Joseph Votel said the fight against the terror group is "not over" and warned ISIS could regroup after US troops leave.

"I was not aware of the specific announcement. Certainly we are aware that he had expressed a desire and intent in the past to depart Iraq, depart Syria," Votel said during a Tuesday hearing held by the Senate Armed Services Committee.

"So you weren't consulted before that decision was announced?" Sen. Angus King, I-Maine, asked.

"We were not, I was not consulted," Votel responded.

In December, Trump tweeted, "We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency," later releasing a video where he said US troops are "all coming back, and they're coming back now."

That decision prompted the resignations of Secretary of Defense James Mattis and the Special Presidential Envoy to the Counter-ISIS campaign Brett McGurk.

Fight against ISIS 'is not over'

"The fight against ISIS and violent extremists is not over, and our mission has not changed," Votel said.

He said ISIS still controls about 20 square miles of territory in Syria where the terror group still commands approximately 1,000 to 1,500 fighters.

Votel would not commit to a timeline for the withdrawal. "I am not under pressure to be out by a specific date," he said.

"The fact the President made a decision and we are going to execute his orders here to withdraw forces from Syria and as we do that we're going to do that in a very deliberate manner," Votel added.

The Syrian Democratic Forces, backed by US air and artillery strikes, are seeking to drive ISIS from this last area of territory but their advance has been slowed as they have encountered refugees fleeing the area.

A Defense Department Inspector General report published Monday said that "absent sustained [counterterrorism] pressure, ISIS could likely resurge in Syria within six to twelve months and regain limited territory."

"We do have to keep pressure on this network, it is a resilient network. It does have certain components that are still left in it, although they are dispersed and disaggregated they have the capability of coming back together if we don't," Votel said.

Asked how the US would maintain such pressure after withdrawing the 2,000-plus troops currently in Syria, Votel said "that is an aspect of the ongoing planning that we are pursuing right now."

"I won't speculate publicly here about things we might do but there are certainly different ways we can do this, working with partners, working with our own capabilities to continue to keep pressure on this network which I think is absolutely vital," he added.

Votel also said that "a key task" that the US was looking at was "the protection of those who have fought valiantly with us and ensuring that they remain safe as our diplomats and United Nations and others pursue a political solution here in Syria," referring to the Kurdish-led Syrian Democratic Forces.

Iraq mission unchanged

Votel said that he has not been given "additional tasks" with regard to the US military mission in Iraq.

In an interview that was taped Friday, Trump told CBS News that the US would use a base in Iraq as a means to "watch" Iran.

"One of the reasons I want to keep it is because I want to be looking a little bit at Iran because Iran is a real problem," Trump said, adding that he wouldn't use the US military outpost to strike Iran, but to "watch" it.

Asked by Sen. Tim Kaine, D-Virginia, if the US mission in Iraq is to defeat ISIS, Votel replied, "that is exactly my understanding," adding that the US is in Iraq at the invitation of the Iraqi government.

Iraqi officials have criticized Trump's comments, saying that the US was in Iraq at the invitation of Baghdad and that its military presence should not be used against Iran.

Defended US support for Saudis in Yemen

Votel also defended US support to the Saudi-led coalition battling the Iranian-backed Houthis in Yemen.

"Certainly it is a very significant humanitarian disaster in Yemen but I do believe departing from our partners there removes the leverage that we have to continue to influence them, which I think we have used in a positive manner and I think it further endangers Americans in the region," Votel said.

His comments come amid renewed efforts in both the House and Senate to block US support to the Saudi-led coalition.

While the US military stopped providing aerial refueling to coalition warplanes in November, the US continues limited intelligence sharing aimed at countering Houthi missile and drone attacks against Saudi Arabia and the United Arab Emirates.

Asked about a recent CNN report detailing how US supplied military equipment provided to Saudi Arabia and the UAE was winding up in the hands of local militias in Yemen, Votel said, "We have not authorized Saudi Arabia or the Emirates to re-transfer any of this equipment to other parties on the ground in Yemen."

"I think we have to look more closely at the allegations in this particular situation to find out what happened," he added.