Defending Indian Wells Masters champion Carlos Alcaraz handed Jannik Sinner his first defeat of the year to advance to the men's singles final with a three-set comeback triumph.

Coming into Saturday's mouthwatering semi-final, Australian Open winner Sinner boasted a 16-0 record for the season and had won 19 straight matches overall, the record for an Italian player in the Open Era.

In a repeat of last year's Indian Wells semi-final - which Alcaraz won in straight sets - Sinner was on course for consecutive win number 20, but the Spaniard rallied to prevail 1-6 6-3 6-2 after a three-hour rain delay.

Alcaraz's fightback triumph saw the world number two make his sixth Masters final on the ATP Tour, and the 20-year-old remains on course for back-to-back Indian Wells successes, a feat last achieved in the men's singles by Novak Djokovic, who won three in a row from 2014 to 2016.

In addition, Alcaraz has now joined Djokovic and Boris Becker as just the third male player under 21 to reach two straight Indian Wells finals, and he now boasts 25 wins over top-10 players on the ATP Tour.

"I stayed strong mentally. I think that's a really important part in this game. You have to be strong mentally if you want to overcome these kind of matches, a set down against someone that's playing an unbelievable game," Alcaraz said on the court after his victory.

"I'm really happy with the things that I've done after that. I changed my style a little bit, I changed my game a little bit and I think it worked very well. I'm really happy to beat Jannik and be in the final again."

After coming up trumps in his semi-final rematch with Sinner, Alcaraz will now square up to a vengeful Medvedev, who lost last year's final to his Spanish foe and also had to recover from a disastrous first set on Saturday.

The Russian ended the USA's hopes of singles glory in California with a 1-6 7-6[2] 6-2 win over 17th seed Tommy Paul, thereby advancing to his 10th ATP 1000 final and giving himself a shot at payback against Alcaraz.

Medvedev did not register a single hold in the first set and let a 4-0 lead slip in the second as Paul managed to force a tie-breaker, but the Russian held his nerve in the decider and broke right away in the pivotal third set.

Paul lost serve once again in the fifth game to fall 1-4 down, and while the home favourite brought up four break points across Medvedev's final two service games, he failed to convert any of them and bowed out on an unforced error on his opponent's first match point.

Alcaraz eased past Medvedev 6-3 6-2 in last year's Indian Wells men's singles final, but before the pair reunite on Sunday evening, Iga Swiatek and Maria Sakkari will compete for glory in the women's showpiece event.