After a comfortable and confident run, Olympic champion and 2017 world leader Dalilah Muhammad emerged from the 400m hurdles semi-finals as a strong favourite for Thursday evening's final.
The 27-year-old cruised to victory in the third of three semi-final heats in 55.00, barely winded by the effort, in a round that witnessed few major casualties.
"I've had a lot of up and downs so I'm just pleased I could qualify like that," said Muhammad, whose 52.64 victory at the US championships was the fastest performance in the world since 2011. "But I have faith that I'll be able to put in a good performance in the final. I've done it before and have the experience of a major final."
Sage Watson of Canada was second just 0.05 back to advance automatically with Eilidh Doyle, the British team captain, third in 55.33, and advancing as one of the two fastest losers.
But Muhammad will have to keep an eye out for Czech Zuzana Hejnova, who's rounding into shape at the ideal time in her bid for a third straight title. The 30-year-old cruised through the finish to take the first heat in 54.59, the evening's quickest time.
"There were no problems but it will have to be much faster in the final," Hejnova said, suggesting the winner will need to run at least 53.30 to take the title.
Kori Carter of the US moved on behind her in 54.92.
Heat two was the closest with Jamaican Ristananna Tracey holding off the fast charge by Swiss Lea Sprunger 54.79 to 54.82. Behind them Cassandra Tate of the US moved on as well in 55.31.
Notable non-qualifiers include Denmark's Sara Slott Petersen, last year's Olympic silver medallist, who clocked 55.45 behind Tate, and Shamier Little, the 2105 silver medallist, who was a distant fourth in the first heat in 55.76.
Bob Ramsak for the IAAF