Armstrong's time of 35 minutes and four seconds for the 26.1km course was 25 seconds better than defending champion Karin Thurig of Switzerland. American Christine Thorburn was third.

Armstrong, 33, told reporters she shared the same determination as namesake Lance Armstrong, winner of the Tour de France a record seven times.

"We share the same last name but were not related but I see similarities we both have," she said.

"We're both very determined and strive for the highest goals with the same focus.

"We're both good time trialists because we both competed as triathletes before focusing on cycling.

"I look up to Lance because he's done a lot for cycling in the USA and around the world. I hope I can keep the Armstrong name flying now that he's retired."

Armstrong used her strength on the climbs in the first half of the course to gain a decisive lead on Thurig.

"I knew that the first half of the course was going to be the key to winning because of my style of racing," she said.

"I had to make as much time as possible out there because I knew Karin would be fast on the descent."

"It was one of the hardest world championship courses I've done."

Armstrong will also compete in the 132-km women's road race on Saturday.