Khaleb McRae ran 400m in 44.52 seconds to break the indoor world record on Friday, 0.05 seconds faster than fellow American Kerron Clement's mark set 21 years ago.
McRae, 25, shaved 0.1 seconds off his personal best as he left second-placed William Jones 1.11 seconds behind at the Tyson Invitational in Fayetteville, Arkansas.
Clement set his record on the same track in 2005.
"Michael Norman (44.52) and Christopher Morales Williams (44.49) have posted quicker times, but neither could be ratified for record purposes," World Athletics wrote on their website.
The 400m outdoor world record belongs to South Africa's Wayde van Niekerk, who ran a time of 43.03 seconds at the 2016 Olympics.
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