Three-time Tour de France winner Chris Froome says the next few days of racing will be "the greatest challenge of my life".
With the race to Paris ending on Sunday, the Team Sky rider has a lead of just 18 seconds over Fabio Aru from Astana, while Rigoberto Uran and home favourite Romain Bardet are also within touching distance of the yellow jersey.
"This is the closest Tour I've ever been in," Froome told Sky News at his hotel in Le Puy En Velay, south-central France.
"This is certainly the greatest challenge of my life.
"I've got to focus on what I'm doing now and not worry about the other guys trying to take that jersey from me."
The Briton added: "I had a mechanical issue on Saturday and I actually thought that was my race over, there and then.
"But I had amazing support from my team-mates and Michal (Kwiatkowski) gave me a wheel. I got going and we're still in yellow."
The reigning champion has just signed a new two-year contract that keeps him at Team Sky until 2020, a show of commitment, he says, after a difficult time for the racing outfit following a UK Anti-Doping investigation.
"I certainly have my faith in the team," said Froome.
"I've seen nothing untoward or dubious. There has been this picture painted of us (in the media), but come meet us, look around.
"This is just a great team of guys trying to do things the right way."
If Froome makes it to Sunday's processional stage in yellow, he will have won cycling's most prestigious race four times and made it a personal three in a row.
He said: "I'm not thinking too much about that right now, but when you look at names like Merckx, Hinault and Indurain who all won it five times... that's really exciting."