Flora Duffy is just one race away from a maiden ITU World Triathlon Series title after finishing fourth in a race dominated by the United States in Edmonton on Sunday.

Duffy leads the rankings with 4,124 points ahead of Katie Zaferes, of the US, who is breathing down the Bermudian’s neck after a podium finish in Alberta, on 3,650 and compatriot Gwen Jorgensen third with 3,325.

Jorgensen, the reigning two-times champion, decided to miss Sunday’s race having stormed to victory at the Olympic Games in Rio de Janeiro two weeks ago.

Duffy is expecting a tough battle to protect her position as the leader in the Columbia Threadneedle Rankings heading into the Grand Final in Cozumel, Mexico, where points count for double.

“I think there will be a little bit of math done to see what needs to be done in Cozumel,” said Duffy, competing for the first time since finishing eighth in Rio.

“I would love to win the series, it’s been really cool to have strong numbers all year.

“But realistically, I never expected it. So whatever happens in Cozumel, it’s been a fantastic year.”

Duffy, whose splits were 9:01 for the 750 metres swim, 29:03 for the 10km bike and 17:17 for the 5k run for an overall time of 57:10, just missed out on the podium after being chased down by Zaferes who came third.

For the third time in history, the US women completed a clean sweep with Summer Cook claiming victory in her first visit to the podium and Sarah True taking second.

“For me a lot of today was just finding the mental willpower to keep myself in the race and put myself in the position to have a strong result,” Cook said.

“I DNF’d last year with hypothermia. I knew I had to come in today extra prepared for the conditions.

“I didn’t think I had a chance at all on the last curve on the last lap and then I started to believe that I had a chance.”

The US team shone from start to finish in Edmonton, with five of the top-ten women out of the swim — including Duffy — sporting the red, white and blue uniform.

Midway through the bike, the chase, which included Britain pre-race favourites Vicky Holland, Non Stanford, and Jodie Stimpson, chipped four seconds off the gap to pull within 26 seconds. However, the leaders undid the chasing group’s hard work on the next lap for a 31-second advantage going into the bell lap.

A slow transition cost Duffy a five-second deficit, with Kristen Kasper the chief beneficiary, with the US athlete taking top position before her team-mate True began to push the pace early on.

Desperate to turn last year’s Edmonton silver into gold, Duffy did plenty of work to catch up to the US women, running as a trio until True took off.

However, a surge from Cook, who had struggled to stay in the lead group on the bike, enabled her to run the field down late on.

As she passed Zaferes, then Duffy, she had only to pick off True, which she did in the final 500 metres. True sealed second to redeem a disappointing performance at the Olympics, where she was forced to withdraw.

The WTS Cozumel will be on September 17, with 1,600 points awarded to the winner, 1480 for second and 1370 for third.

• Tyler Smith and Erica Hawley both finished seventh in their triathlons in the Canadian Junior Elite Series in Edmonton, Alberta, on Saturday.

Smith, 17, competing in the 16-19 junior men’s race, posted a time of 58min 11sec — a little more than a minute behind winner Pavlos Antoniades, of Canada, who crossed the line in 57:02.

Smith completed the 750 metres swim in 8:53, the 20km bike in 30:52 and the 5km run in 16:46.

He had been hoping for a top-five finish after his impressive fourth place at last month’s Quebec Provincial Championships, an event turned into a duathlon because of the poor water conditions.

Brennen Smith, of Canada, came second in 57:07, with his compatriot Luke Hanson completing the podium in 57:16.

Hawley finished in 1:06:11 in the junior women’s race — more than four minutes behind winner Desirae Ridenour, of Canada, in 1:01:57.

Sophie Malowiecki, of Australia, was second in 1:02:08 while Hannah Henry, of Canada, placed third in 1:03:10.

Hawley finished the swim in 10:08, the bike in 34:22 and the run in 19:54.

The 18-year-old, who recently started as a freshman at Boulder University, has had several top-ten finishes this season.