Australia's Rohan Dennis took a razor-thin victory on the opening day individual time-trial at the Tour de Suisse on Saturday.

Bahrain-Merida's Dennis, who beat Tom Dumoulin at the 2018 time-trial world championships, completed the 9.5km high-altitude course in 10min 50sec.

The entire top ten were within 11 seconds of each other as Poland's Maciej Bodnar was second and another Australian, Sunweb's Michael Matthews, was third.

For Dennis the victory is his first since joining Bahrein from BMC.

"This is a step forward and we're only going in one direction from here," said Dennis.

"There's still the rest of the week and the time trial later in the week is a goal of mine too. And then there's the Tour de France. I'm looking forward to it," he said.

Of the overall contenders for the eight-stage run through the Alps, Tour de France champion Geraint Thomas, a powerful time-trialer, was fastest. His young Ineos teammate the talented Colombian all rounder Egan Bernal, was just six seconds behind him.

"I'll refuel at the at the hotel tonight," said Thomas, admitting he never expected to challenge for the win on Saturday.

"There's a big eight days to come. Tomorrow is a new day and we're looking forward to getting back on the bike and giving our all."

Bora leader Peter Sagan, who has had a quiet spring, was seventh Saturday. 

He is capable of a surprise on Sunday when the real hostilities could begin on a stage that loops three times around Langnau on a circuit that contains two mountain passes.