The declaration was so important for the President that he had his Press Secretary read his tweets to reporters at the start of Wednesday's White House briefing.
“So, that was directly from the President - we spent some time working on that,” Press Secretary Kayleigh McEnany said to reporters.
The announcement by the President came amid of flurry of actions by the Pentagon in recent days with respect to the Confederacy, and the Civil War.
Last week, the Marine Corps announced the details of a ban on the display of the Confederate Flag by any personnel on military bases.
On Monday, the Army floated the idea of renaming bases like Fort Bragg, Fort Hood, and Fort Benning, all named for soldiers who fought with the South, and against the Union.
Then on Tuesday, the Navy said it would also ban the display of any items which bear the likeness of the Confederate Flag.
Even before this decision, the President had come under political attacks on the Confederate Flag, as a group of GOP activists who oppose Mr. Trump had put together an ad titled, "Flag of Treason."
"Curious which of Trump's "fine" pollsters came up with the idea of litigating the Civil War on the side of the racist, traitorous confederacy," said John Weaver, the founder of Project Lincoln.