Defending 200m world champion Shericka Jackson sent a message to 100m gold medallist Sha'Carri Richardson she will not give her crown up lightly, easing home in front of her in their semi-final on Thursday.
Jackson, silver medallist in Monday's 100m final, timed 22.00sec with Richardson having to battle to edge Ivorian veteran Marie-Josee Ta Lou for the second automatic qualifying spot.
Richardson clocked 22.20sec whilst 2017 world silver medallist Ta Lou went through as one of the two fastest losers for Friday's final.
Ta Lou, 34, said finishing fourth in the 100m final had not been too hard to take as she knew people recognise her talent.
"I do not need a medal to showcase my talent," she said.
"I know I am talented, and I know I will medal, maybe next year. I do not know if I will medal tomorrow, we will see."
Richardson, bidding to become only the fourth woman to do the sprint double, may not even be the USA's favourite for the final.
Olympic bronze medallist Gabby Thomas posted the fastest time of the three semi-finals of 21.97sec.
The 26-year-old, who beat Richardson in the US trials, came off the bend behind Britain's Dina Asher-Smith, but cruised past her to cross the line in 21.97sec.
"I was controlling the whole race and I knew I was going to do a smooth finish and win my heat," said Thomas.
"I feel confident and strong going to the finals tomorrow but there are some things I can improve.
"It has been an unreal time for women's sprinting.
"All athletes are doing amazing things, not only a couple of us, it is everyone.
"I expect a special time from the winner tomorrow, just like it was in the 100m."
The 2019 champion Asher-Smith, disappointed by her performance in the 100m final, took the second automatic qualifying spot after clocking 22.28sec.
"The 100m was definitely a disappointment," said Asher-Smith.
"I am in personal best shape so it hurt a lot.
"But I am still running, not stopping, and now I qualified for another final. It is time to move on and perform a fast 200m."
Julien Alfred produced an assured performance for someone so inexperienced at the top level.
The 22-year-od St Lucia sprinter -- fifth in the 100m -- made her way past three of her rivals to win her semi-final in 22.17sec.
Alfred said it had taken a day to get over missing out on a medal in the 100m but she was rebuilding her confidence.
"I'm just taking it one step at a time and trying to come back," she said.
"I felt good today. I am not really worried about the 200m like I was in the 100m."
Asher-Smith's teammate Daryll Neita also progressed.
Anthonique Strachan of the Bahamas fills out the final spot as the second of the two fastest runners-up.