BEIJING - A challenging white water course could pose serious problems for slalom canoeists and kayakers at the Beijing Olympics where Frenchman Tony Estanguet is seeking his third successive gold medal.

France's Tony Estanguet competes to win the C1 men's race at the ICF Canoe/Kayak Slalom Racing World Championships 2006 in Prague in this August 6, 2006 file picture. Double canoe Olympic champion Estanguet will carry the French flag at the 2008 Beijing Olympics opening ceremony. [Agencies]

Slovakia's Hochschorner twins, Pavel and Peter, are also seeking their third Olympic title in a row in the C2 event and their main challenge will come from compatriots Peter and Ladislav Skantar, also brothers.

Estanguet faces a serious threat from another Slovak, 1996 champion Michal Martikan, in the C-1 class and believes the unpredictable conditions on the Olympic course could be the decisive factor.

"We will find it very difficult to navigate ... on this wild artificial course," Estanguet said. "On a stroke where I normally move two metres, I sometimes moved only 20 centimetres.

"The force of the water means you have to fight."

Another Frenchman, Fabien Lefevre, and Briton Campbell Walsh - the bronze and silver single medallists in Athens four years ago - are likely to be battling for K-1 medals again while Elena Kaliska of Slovakia defends her K-1 single crown.

On the flatwater course, Germany and Canada are favourites after a strong showing during the World Cup season.

In the men's K-1, Canada's Olympic champion over 500 metres Adam van Koeverden will start as the favourite in both the 500 metre and 1,000 metre races, with Britain's Tim Brabants and Norway's Olympic 1,000 metre champion Eirik Veras Larsen likely to challenge.

Canada's Thomas Hall and Germany's three-times Olympic champion Andreas Dittmer could vie for the medals in the C1 over both distances while Germany's Katrin Wagner-Augustin is the one to beat in the women's K1 race.