Postpublished at 13:03 BST 7 June 2019
*Federer 3-6 Nadal
But Federer doesn't look too ruffled as he plays a lovely drop shot to win the first point of the second set.
Nadal outsmarts him, though, lobbing the 37-year-old to bring up 30-30.
World number one Novak Djokovic loses first set 6-2 to fourth seed Dominic Thiem in French Open semi-final but takes second 6-3
Thiem leads 3-1 in third set when play is suspended because of rain
Winner will face defending champion Rafael Nadal, who beat Roger Federer 6-3 6-4 6-2
Britain's Johanna Konta loses 7-5 7-6 (7-2) to Czech teenager Marketa Vondrousova in women's semi-final
Vondrousova will face Ashleigh Barty in Saturday's final after the Australian eighth seed beat Amanda Anisimova in three sets
Becky Grey and Saj Chowdhury
*Federer 3-6 Nadal
But Federer doesn't look too ruffled as he plays a lovely drop shot to win the first point of the second set.
Nadal outsmarts him, though, lobbing the 37-year-old to bring up 30-30.
*Federer 3-6 Nadal
Greg Rusedski
Former British number one on BBC Radio 5 Live
They've put a lot of water on the court to stop the clay from blowing about - that should be to Rafa's advantage.
Federer 3-6 Nadal
Rafael Nadal has won 91 matches in Paris in the last 14 years. And now Roger Federer is a set down against him.
Federer 3-6 Nadal
Greg Rusedski
Former British number one on BBC Radio 5 Live
Federer should have come in for the point which led to set point.
The angle, power and speed Nadal can play with the double-handed backhand is amazing.
It was a spectacular set of tennis from the Spaniard.
Federer must be wondering what he needs to do to win the match.
Federer 3-6 Nadal
Wow. Wow. WOW.
Nadal finishes the set in style. He hits an 84mph cross-court backhand and there is nothing 20-time Grand Slam champion Federer can do.
Federer 3-5 Nadal*
'Vamos,' shouts Nadal as Federer hits the ball long. A second set point.
Federer 3-5 Nadal*
Nadal's backhand catches the top of the net and lands wide. Back to deuce.
Federer 3-5 Nadal*
Nadal quickly regains control and it's suddenly set point.
Federer 3-5 Nadal*
Federer whizzes a cross-court forehand and it goes out of Nadal's reach. The Spaniard hits the ball long. 15-30.
It's easy to forget Federer's age sometimes because he barely breaks into a sweat after these long rallies. He turns 38 in August. That's two years off 40. Let that sink in.
Federer 3-5 Nadal*
Dramatic scenes as the wind picks up and blows red dust up around Federer. That was like something out of a Western movie.
Federer 3-5 Nadal*
It's not the nicest day in Paris but the stands are filling up now. The French Open crowds aren't always on time, but they get there eventually. You wouldn't want to miss a minute of this.
Federer isn't letting this match get away from him. He holds to love.
Nadal has not faced Federer at the tournament since the 2011 final, when he won in four sets, while the Swiss took just four games off his rival during their last meeting on the surface in Rome in 2013.
"I'm very happy to play Rafa, because if you want to achieve something on the clay, inevitably, at some stage, you will go through Rafa," added Federer.
*Federer 2-5 Nadal
These two have a combined age of 70, but you wouldn't know it the way they're racing round the court.
Nadal sprints to the net to bring up 40-15. The 33-year-old hits a ball long, but then comes out on top of a lengthy rally to hold.
Federer 2-4 Nadal*
Greg Rusedski
Former British number one on BBC Radio 5 Live
These guys, with the conditions so brutal, are actually making very few unforced errors.
Federer 2-4 Nadal*
It took six break points, but Nadal converts as Federer hits the ball into the net.
The 11-time French Open champion allows himself a fist pump in celebration as he goes a break up again.
*Federer 2-3 Nadal
Nadal loses a third break point, Federer serves an ace but AGAIN the Spaniard brings it back to deuce.
Both players are at the net but Federer blinks first. If this game finishes in under four hours, I'll be very surprised.
*Federer 2-3 Nadal
Plenty of grunting from both sides of the net, and a cheer as Nadal's backhand does not make it over. Another break point saved.
*Federer 2-3 Nadal
An 11-shot rally goes Federer's way as Nadal's backhand lands wide of the whitewash. Break point saved.
But then Federer's ball lands outside the tramlines and Nadal gets another go. Second break point.
*Federer 2-3 Nadal
The contrast between these two is beautiful to watch. Federer hits his stylish backhand, which Nadal returns with a brutish forehand.
Break point Nadal.
*Federer 2-3 Nadal
Oops. Federer hits a forehand up into the stands. Is the wind playing with him?
Both players' hair shows how gusty it is out there. Their long locks are all over the place.