The United States broke their own world record in the 4x400 mixed relay in the opening heats at the Olympics on Friday, crossing the line in three minutes 7.41 seconds amid a party atmosphere at the purple Paris track.

They set the previous mark of 3:08.80 at the 2023 World Championships in Budapest.

The U.S. led midway through the second lap in a text book performance, overcoming a fast field in the opening heat in which four national records were broken as well as the world mark.

"I always knew we were going to run fast, and we talked about how it was going to take a record to win a medal," said American Shamier Little. "It took a record to win our prelim."

The French team were willed across the finish by a partisan home crowd, as they held off Belgium (3:10.74) and Jamaica (3:11.06) to finish second in 3:10.60 in the rarely contested event.

The crowd had to be shushed as they chanted for the French team on the first day of the athletics programme at the Stade de France and they broke into a loud roar as France took a slender lead.

Little pulled ahead for the U.S., however, and Bryce Deadmon extended the lead.

The Americans were eager to avoid the drama of three years ago, when they were disqualified from the Olympic final – and later reinstated due to an official's error – before eventually claiming bronze.

Kaylyn Brown was all business through the final lap, however, crossing the finish line on her own and the Paris crowd willed Amandine Brossier over the line in a thrilling finish down the final straight.

In the second heat, Britain advanced in a national record time of 3:10.61 and the Netherlands also qualified.

The Dutch will be hungry for redemption after their performance at the World Championships last year, where Femke Bol nearly brought home the gold but fell five metres from the line, hitting her head and dropping the baton.

The heats set the tone for the evening programme, where a packed out cheered wildly for home hopes in a stark contrast to three years ago, when competitors ran in front of empty stands in the COVID-quieted Tokyo Games.

"This is completely different compared to 2021 just for the simple fact that we have fans out here. I was running down the curve and I was like, 'Ah damn, it's kind of loud in here'. It's a great experience," Deadmon told reporters.

The 4x400 mixed relay final is set for Saturday.