Australia's youngest-ever Olympic whitewater kayaker, Jess Fox, warmed up perfectly for the London Games by successfully defending her world junior slalom title in the United States.

The Sydney 18-year-old emerged as the top paddler at the junior world titles on the Wisconsin River at Wausau with three gold medals, including a dominant victory in her Olympic K1 event.

Fox took out the junior women's K1 and C1 race double as well as the Under-23 C1 team event with Australian teammates Ros Lawrence and Alison Borrows.

She leaves for London on Tuesday and will start the Games competition as a fringe medal contender at the Lee Valley Whitewater Course in the July 30 heats.

The daughter of former world champions Richard and Myriam, Fox felt the success had her well primed to handle the pressure of her Games debut.

She won through to the Monday morning (AEST) final with strong heat and semi-final victories before comfortably retaining the K1 crown she won at age 16 in 2010 with a one-second margin despite one gate touch in the final.

Fox made the finals of all three senior World Cup races last month - finishing sixth, seventh and eighth - in a promising start to a campaign which has her ranked No.5 on current standings.

But she felt the ability to handle the pressure of being the favourite at the junior worlds would stand her in good stead in London.

"It was a different kind of pressure on me and I also had the pressure I put on myself," Fox told AAP.

"It was a real confidence boost in the lead up to the Olympics."

Fox is aiming to become Australia's first whitewater Olympic champion and the third medallist in the women's K1 after Danielle Woodward (1992) and Jacqui Lawrence (2008) both grabbed silvers.

NZ Newswire