Shanghai, China: Noah Lyles launched himself from near the back of the field to beat fellow American Christian Coleman by just 0.006secs and win the 100 metres at the Shanghai Diamond League on Saturday.
Lyles's blistering 9.86sec was the best time this year and a personal best, and lays down a marker ahead of the world championships in the autumn and the Tokyo Olympics next summer.
The 21-year-old, part of a new generation of American sprinters, ducked to the line with a glance to his left to Coleman. A photo finish confirmed Lyles had won.
Third was South Africa's Akani Simbine and fourth last year's Shanghai victor, Britain's Reece Prescod.
It is early days in the season, but Lyles and his rivals are already eyeing the Doha world championships in September while the 2020 Tokyo Games also loom.
Lyles, the 200m Diamond trophy winner last year, celebrated wildly and said: "In pre-season I'd taken a couple of losses, a couple of second places, even on my home track, so I really wanted to come out here and told my coach I wanted to do something.
"I told him that today is the day, today is the day we put it all together."
Asked by AFP what message his nail-biting win sent to the rest ahead of a crucial 14 months, Lyles said: "I really wanted to make sure that this year everybody knows that I'm a 100m and 200m runner, not just a 200m runner who's kind of running the 100m."
In the women's 100m, Aleia Hobbs of the United States, running out of lane seven, streaked home clear of the field for victory in 11.03sec.
Jamaica's world and Olympic 110m hurdles champion Omar McLeod collapsed crying on the track and had to be consoled by his rivals after his fourth victory in as many appearances in Shanghai.
The 25-year-old, winner in 13.12 sec, said: "It was difficult for me mentally to compete today.
"My auntie died yesterday. But then I asked myself, 'what would she want?'
"And she would want me to race."
In a highly anticipated match-up, Qatar's Abderrahman Samba overtook his flagging American rival Rai Benjamin over the last hurdle to win the men's 400m hurdles.
Samba, the second-fastest man in history in the event with his 46.98sec last year, was already the quickest this year and his 47.27 lowered his previous mark.
It was the first time that the Saudi-born Samba and rising prospect Benjamin -- the joint third-fastest ever and still aged only 21 -- had faced one another.
"It was a great race and Rai and I pushed each other to the line," said a smiling Samba, 23.
"The main goal is the world championships (in Doha) later this year.
"This year is a big year and I feel better this year."