"I was not aware" before Trump made his troop-pullout announcement, he added, while saying that Central Command was 'aware he had expressed a desire and intent in the past.to depart Syria'.
He went on to say he'd keep troops in Iraq to be able to "watch Iran", which elicited a strong reaction from Iraqi President Barham Salih.
Under questioning from Senator Elizabeth Warren of MA, a Democratic presidential contender, Votel said that "we have no observations of our own" to confirm an Associated Press report of torture and abuse in detention centers in Yemen operated by the United Arab Emirates.
A US -led coalition has eliminated some 99 percent of the territory in Syria and Iraq that the Islamic State, or ISIS, once claimed as its so-called caliphate.
"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.
President Trump, however, told an American news channel on Sunday that such rebukes could not force him to change his mind.
Trump announced in December that "all" USA forces would be leaving Syria "now".
"We are working through a variety of planning scenarios for how we would potentially do, continue to maintain pressure on ISIS as we withdraw out of Syria", Votel told the committee.
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Trump also tasked the Pentagon late previous year to start making plans for cutting the US force in Afghanistan in half.
The tensions in the region will likely be one of Trump's key points in his State of the Union address.
The discussions have focused on the US withdrawing its troops in return for Taliban assurances that terrorist groups including al-Qaeda and Islamic State won't be allowed to operate from Afghanistan.
He said: "The US presence in Iraq is a part of an agreement between the two countries with a specific task which is to combat terrorism".
The command added that ISIS "may conduct opportunistic attacks on US personnel as they withdraw" and posited that the group's leaders "will leverage the event as a "victory" in its media".
"When America's national security and vital interests are at stake, some circumstances require not only the use of important diplomatic tools but also direct involvement from the United States", he said.
Taking aim at Trump and the U.S., Salih added: "Don't overburden Iraq with your own issues".
In his opening remarks, Votel said, "The fight against ISIS and violent extremists is not over", but added that US ground forces will depart Syria "in a deliberate and coordinated manner".
He said that about 1,500 to 2,000 ISIS fighters remain in a 20-square-mile pocket in Syria near the Iraqi border.