Chris Hoy's preparations ahead of his attempt to break the world kilometre record have been affected after his arrival in La Paz was delayed.
Hoy, 31, is aiming to better Arnaud Tournant's high-altitude mark of 58.875 seconds - but has been stranded in another part of Bolivia.
The BBC's Jill Douglas, who is waiting in La Paz with a documentary team, said Hoy was stuck in Santa Cruz.
Hoy is due to make his world 1km record attempt on Saturday.
Earlier, Hoy had explained how apprehensive he was about the bid.
"There are nerves at pushing myself to the limits at 3,400m above sea-level and the horror stories you hear.
"The apprehension in some part is down to doing something I've never done before at this altitude," he said.
The record attempt - at La Paz's aging Velodromo Alto Irpavi - will be Hoy's last hurrah at the kilo, which has been controversially scrapped from the Beijing Olympics next year.
"There could be a problem if there is any kind of wind"
"All the preparations have gone well - better than expected," he said. "I've not done a lot on the track, more on the static bike.
"There is the weather factor to be considered which I have to say has been a concern.
"There could be a problem if there is any kind of wind. But we won't really know that until we pedal on to the track.
"I've been told that they are now expecting more than two thousand spectators on Saturday which should generate some atmosphere.
"But I can't be sure whether they are turning out to see a world record being broken or a madman in action!"
Hoy's Olympic record of 1.00.711, set in Athens, is the fastest time ever at sea level.