Rafael Nadal will play Andy Murray or Novak Djokovic in the Rome Masters final after beating Richard Gasquet.
The world number one broke the French 16th seed to lead 6-5 before surviving a few wobbles to take the first set.
Nadal, eyeing a sixth Italian title in seven years, raced through the second set for a 7-5 6-1 win as Gasquet faded.
Murray, the first Briton to reach the semi-finals in Rome since 1932, and Djokovic will play at 1900 BST for the right to face Nadal in Sunday's final.
The opening set proved to be a stern test for Nadal, who ensured he remained top of the rankings ahead of Djokovic by reaching the last four.
Gasquet, buoyed with wins over Roger Federer in round three and Tomas Berdych in the quarter-finals, wasted three break points in three different games as he troubled the Spaniard with an array of backhand winners and aggressive net play.
But after squandering chances at 5-5, Gasquet had no answer to his opponent's serve to lose the first set.
Nadal ruthlesssly took full advantage of the tiring Frenchman, breaking his opening service game in set two, and with two other breaks of serve, the victory was swiftly wrapped up.
"It was a complicated situation on my serve in the first set but I managed to pull through," the 24-year-old Nadal said. "I'm happy to make the final after a difficult week."
The top seed had almost withdrawn earlier in the week as he struggled with illness and then needed three sets to overcome Italian qualifier Paolo Lorenzi in round one.
And having improved his career record in Rome to 31-1, with his only loss against compatriot Juan Carlos Ferrero three years ago, Nadal was looking forward to facing Murray or Djokovic.
Djokovic has beaten Nadal in all three finals they have contested this year, including at the recent Madrid Open, when the Serb secured his first victory over the Spaniard on clay.
"Every aspect of the game will be important," Nadal added regarding a potential showdown with Djokovic again. "I know he is playing at an exceptional level right now but I just have to fight to the end like I always do.
"If I don't beat him Sunday, then the next match. I'm happy with my clay-court season. How I'm playing in the last couple of matches is the way forward, more aggressively."
BBC Radio 5 live sports extra will have live commentary of Murray's semi-final from 1900 BST, while the BBC Sport website will have live text commentary.