A reporter asked if the president was "just kidding" when he said he would slow down testing at his rally on Saturday in Tulsa.
"I don't kid... let me make it clear. We have got the greatest testing program anywhere in the world," Trump responded.
The Republican president said at a political rally in Oklahoma on Saturday that he had directed his people to slow down testing for the virus because the process had led to an increased number of known COVID-19 cases.
The White House on Monday said at the time that he was kidding and made clear that no such request was made.
"It was a comment that he made in jest," White House press secretary Kayleigh McEnany said at a news briefing. She said Trump had not told officials to slow the rate of testing. "He has not directed that," she said. "Any suggestion that testing has been curtailed is not rooted in fact."
Trump sees numerical measures as signs of victory or failure. He has repeatedly lamented the fact that better U.S. testing has led to a higher known number of identified coronavirus cases across the country.