Veteran American Kristin Armstrong completed a remarkable Olympic cycling hat-trick of gold medals by winning the women's 29.7km time-trial in Rio on Wednesday.

Just a day before she turns 43, Armstrong added to her gold medals from Beijing and London to become the first cyclist to win three Games titles in the same discipline.

In wet and windy conditions, she posted a time of 44min 26.42sec to edge out Russian Olga Zabelinskaya, who only returned from an 18-month doping suspension last year, by 5.55sec, with Olympic road race champion Anna van der Breggen of the Netherlands third at 11.38sec.

Armstrong hit the first time check atop the 1.3km Grumari climb after 10km with a 4.9sec lead over Elisa Longo Borghini of Italy and 6.32sec to Van der Breggen.

Zabelinskaya was sixth then but by the second, at the top of the 2.1km Grota Funda climb and 10km from the finish, she was first, 2.88sec ahead of Armstrong with Longo Borghini third at 6.98sec.

Armstrong, though, finished the strongest and pulled back the time she'd lost on the second climb to streak down the final descent and claim the gold medal.

The treacherous conditions caught out 2013 world champion Ellen van Dijk, who skidded off the road and into a ditch, although without hitting the deck.

That mistake perhaps cost the Dutch rider a medal as she finished fourth, just 11sec behind her team-mate Van der Breggen.