Sydney McLaughlin-Levrone and Femke Bol eased through the opening round of the women's 400m hurdles on Sunday to remain on a Paris Olympics collision course.
US star McLaughlin-Levrone, the reigning Olympic champion and world-record holder, cruised through her heat to win in 53.60sec at a sun-baked Stade de France.
The Netherlands' current world champion Bol shrugged off the after-effects of her dazzling performance in Saturday's 4x400m mixed relay to coast through her heat in a leading 53.38sec.
The showdown between the pair promises to be one of the highlights of the athletics programme in Paris, pitting the two fastest women in the history of the event against each other.
The rivals are the only two women to ever run under 51 seconds for the event.
McLaughlin-Levrone, competing in her third Olympics at the age of 24, has not been beaten over the distance since her silver medal at the 2019 World Championships in Doha.
Despite only limited appearances this season, the Los Angeles-based star has been in blistering form, smashing her own world record with a time of 50.65sec at the US trials in Eugene in June.
McLaughlin-Levrone did not need to get out of second gear in Sunday's heat, easing up well before the finish line to qualify for Tuesday's semifinals comfortably in her first outing since her world record-breaking display.
"It was good to just shake the rust off," McLaughlin-Levrone said. "I haven't raced since US trials. The track is pretty fast and just feels good just to get back out there and compete."
NOMINATED AS CAPTAIN
McLaughlin-Levrone is the captain of the USA athletics squad in Paris, a role that she was nominated for by her teammates.
"Honoured to have that role," she said. "It's great to know that my peers respect me as a competitor. I'm hoping to represent Team USA as best as I can."
Bol showed no sign of fatigue after Saturday's relay heroics, when she overcame a deficit of around 15 metres at the final changeover to run down the USA quartet and clinch gold.
The Dutchwoman, a bronze medallist in Tokyo three years ago, won gold at last year's world championships in Budapest in the injury absence of her American rival.