London Marathon winner Kelvin Kiptum, with the second-fastest time in marathon history, could challenge the world record in Sunday's Chicago Marathon while Ruth Chepngetich seeks a record third consecutive women's title.
More than 47 000 runners are expected to race over the streets of Chicago but much of the focus will be on 23-year-old Kenyan Kiptum as he seeks a third title in as many starts over the 26.2-mile distance.
Kiptum won in April at London in two hours, one minute and 25 seconds to finish 16 seconds off the world record set by compatriot Eliud Kipchoge in winning the 2022 Berlin Marathon.
Kiptum, who also won his marathon debut last December at Valencia, says he can crack 2:01:00 when in peak form even as he denies the world record is in his plans in Chicago.
"When I have trained well, and I am healthy, I can run 2:00," Kiptum told Olympics.com.
"The world record is not in the plan for now, but in the future I know I can run 2:00 or something like that."
Kiptum, who turned down a chance to run for Kenya at the World Athletics Championships to better prepare for this race, faces a Chicago course with a minimal elevation rise that could help world-record efforts.
"I have trained really well for Chicago, and I know that Chicago is fast, but I'm just looking forward to testing the course," Kiptum told the Olympic website.
"I trust myself and my target is to just run a good race and run under the course record."
That mark is 2:03:45 set by Kenyan Dennis Kimetto in 2013.
Chicago has seen the men's world record broken twice, but not since Morocco's Khalid Khannouchi in 1999, and the women's world record shattered three times, most recently the 2:14:04 by Kenyan Brigid Kosegi in 2019.
Kenya's Chepngetich is trying to complete a "three-peat" after winning last yer in 2:14:18, what is now the third-fastest women's marathon time behind Kosgei's race record and the women's world record of 2:11:53 set by Ethiopian Tigst Assefa in winning last month's Berlin Marathon.
Also in the field are Kenya's Joyciline Jepkosgei, the 2019 New York Marathon and 2021 London Marathon winner, and London champion Sifan Hassan, the Tokyo Olympic champion at 5 000m and 10 000m.
HASSAN LIKES CHALLENGE
Dutch standout Hassan made a late charge to win in London in her marathon debut in 2:18:33 and just 41 days later won a 5 000- and a 10 000-metre title at a Dutch meet.
Six weeks after running three distances at the world championships, taking silver at 5 000m and bronze at 1 500m while falling while leading the 10 000m final, Hassan will race in Chicago unsure how she will fare.
"I like to be challenged," Hassan said. "I have the experience from London so I'm looking forward to see what the marathon can teach me this time."
Defending champion Benson Kipruto could become the first back-to-back men's winner in Chicago since compatriot Samuel Wanjiru in 2009-10.
Also in the men's chase are Ethiopian Seifu Tura, the 2021 Chicago winner and last year's runner-up, and Belgian Bashir Abdi, the European record-holder in 2:03:36 who was third at the Tokyo Olympics.