(fixes typo in slug). Rome, July 17 - Three-time winner Chris Froome is the favourite to add a fourth Tour title this year, second-placed Fabio Aru of Italy said on the race's second rest day Monday. Froome holds an 18-second lead over the Sardinian after 15 stages and ahead of several Alpine stages where Aru is set to attack and try to win back the jersey he held for two stages. The penultimate stage, on July 22, however features a time trial in Marseille where Froome has the edge. "I think that Froome, given that he has won the Tour de France three times, is the favourite and has the experience to win this year too," Aru said. "He's top of the general classification, he also has a better chance in the Marseille time trial and he also has a very strong team," he said, referring to Team Sky. Froome said: "I knew this year would be the toughest race". The Tour ends in Paris on July 23.