President Trump suggested IS had nearly been eliminated during a speech on Wednesday.
All territory held by so-called Islamic State in Syria has been "100%" eliminated, according to the White House.
It comes after US President Donald Trump has said the last of so-called Islamic State's territory in Syria would soon be freed by US-backed forces.
Press secretary Sarah Sanders told reporters aboard Air Force One that Donald Trump was briefed about the development by Acting Defense Secretary Patrick Shanahan.
There has been no official announcement of Daesh's defeat from forces on the ground.
Speaking on Wednesday, Mr Trump said IS, also known as Daesh, is "not doing so well".
"You know, we took over the caliphate. You’ll see it tonight. When I came in, it was a mess."
Mr Trump spoke as he left the White House and displayed maps of IS-held territory in Iraq and Syria on the day he was elected, up until Wednesday morning.
US-backed fighters battling to retake the last IS outpost in eastern Syria seized most of the last pocket of land on Tuesday.
Mr Trump has previously announced the defeat of the group, but sleeper cells of fighters remain in Syria.
The president said the US will keep 400 troops in Syria indefinitely.
Last month, the White House said around 200 American personnel would remain there on a peacekeeping mission after the rest of its forces are withdrawn.