The top US general in the Middle East has said he disagrees with President Donald Trump's decision to withdraw from Syria.
Gen Joseph Votel told CNN that IS militants were still active in Syria and US-backed forces were not yet capable of handling the threat alone.
The commander told the Senate last week that Mr Trump did not consult him ahead of announcing his Syria pull-out plans.
He is the latest US official to break with Mr Trump over his Syria policies.
During his Friday address from the White House Rose Garden, the president said he would have an update on Syria within the next 24 hours.
"We have a lot of great announcements having to do with Syria and our success with the eradication of the caliphate," Mr Trump said.
But the general leading that battle has expressed a different sentiment.
"[IS] still has leaders, still has fighters, it still has facilitators, it still has resources, so our continued military pressure is necessary to continue to go after that network," Gen Votel told CNN earlier on Friday.
"When I say, 'we have defeated them,' I want to ensure that means they do not have the capability to plot or direct attacks against the US or our allies."
Mr Trump announced in December that "after historic victories" against IS, he would be immediately withdrawing US troops from the region.
His surprise policy shift led to the resignation of Defence Secretary Jim Mattis, further shocking US lawmakers and allies.
Gen Votel said: "It would not have been my military advice at that particular time."
Gen Votel, who is the head of US Central Command, also noted that waiting until US-backed Syrian forces were capable of managing the IS threat on their own was "another key criteria indicating to me that we have accomplished our mission".
"We're not there," he said.
What's the current situation?
The US had led a coalition against IS in Syria along with Syrian Kurdish and Arab fighters, with around 2,000 troops on the ground.
Mr Trump's abrupt announcement last year sparked warnings from within his own Republican party as well as US foreign allies that a hasty withdrawal could help the resurgence of IS.
At the Munich Security Conference on Friday, UK foreign intelligence agency MI6 chief Alex Younger said despite defeats, IS fighters are regrouping.
Mr Younger also expressed serious concerns about dispersing IS militants returning to Europe.
An August 2018 US report noted there were still as many as 14,000 IS militants in Syria and even more in neighbouring Iraq. There is a fear they will shift to guerrilla tactics in an attempt to rebuild their network.