Sha'Carri Richardson failed to advance past the first round in the women's 100m at the US track and field championships in Oregon.

In what is the American team's trials for the World Championships at the same venue in July, the 22-year-old was fifth in her heat.

Richardson, who missed the Olympics in Tokyo last year after testing positive for marijuana, ran 11.31 seconds.

In the men's 100m, Fred Kerley won his heat in a world-leading 9.83secs.

Aleia Hobbs was fastest in the women's 100m after running 10.88secs.

Richardson, who was down in 23rd overall, can still make the World Championships as she is competing in the 200m.

Reigning world champion Christian Coleman was omitted from the Olympics because of an 18-month ban for missing three drugs tests and won his 100m heat in 10.08secs.

He automatically qualifies for the 100m at the World Championships having won the event in Doha in 2019.

"Even though the 100m is the shortest race in track and field so it seems easy, I feel like it's super-hard," said Coleman.

"There's so many opportunities to mess up. You've got to be perfect at this level."

Allyson Felix, who will retire at the end of the season, won her 400m heat in 52.30secs.

"It's tough," said the 36-year-old, who is the most decorated female track and field Olympian of all time.

"I think more than physically, just mentally, emotionally all of that - I think that's been the biggest struggle.

"It's bittersweet for sure. But also, I feel so ready. I don't think I have anything left to give. And when I start to feel that I know it's time."

There were three finals on the opening day of the championships, with Quanesha Burks winning the women's long jump, Brooke Andersen claiming the women's hammer title and Andrew Evans winning the men's discus.