The United States set a new world record in the heats of the mixed 4x400m relay at the Paris Olympics on Friday.
The quartet of Vernon Norwood, Shamier Little, Bryce Deadmon and Kaylyn Brown timed 3min 07.41sec, smashing the previous best of 3:08.80 set when the US won world gold in Budapest last year.
"We wanted to come out here and execute good hand-offs," said Norwood.
"We set the tone for the rest of the United States with that world record."
Little added: "We have a really good group of guys and gals.
"I'm just really excited, first of all for our record, and that's only in the prelim, so it's only up from here."
There were also national records for France (3:10.60), Belgium (3:10.74) and Jamaica (3:11.06) in second, third and fourth places.
Britain won the second heat in 3:10.61, also a national record, ahead of the Netherlands and Italy.
The Dutch quartet did not feature Femke Bol, the 400m hurdles specialist who is aiming for a potential treble gold haul as she is in the squads for both the mixed relay and women's 4x400m relay.
Jamaica and Poland qualified as the two fastest finishers outside the three automatic spots form each heat.
The mixed relay made its Olympic debut at the Covid-delayed Tokyo Games.
Poland took gold in the Japanese capital ahead of the Dominican Republic and the US.
The final is scheduled for 1855 GMT on Saturday.
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