By Pritha Sarkar

PARIS (Reuters) - An 18-year rivalry will play out its next gripping chapter at Roland Garros as Andy Murray and Novak Djokovic eye up a French Open final in which milestones galore will be on the line.

Will Murray become the first British man to lift the French Open trophy in more than eight decades? Or will Djokovic have enough energy left in the tank after playing four days in succession at the rain-ravaged claycourt grand slam to become the first man in almost 50 years to hold all four majors at once?

What is certain though, is that the Musketeers' Cup will have a new name engraved on it come Sunday -- weather permitting -- after Djokovic pulled rank on a player he described as "a leader of a new generation" to reach his fourth Paris final in five years.

The world number one's 6-2 6-1 6-4 win over Austrian tyro Dominic Thiem on Friday had to be staged on the secondary Court Suzanne Lenglen after a week of rain derailed the tournament's usual schedule.

That left Murray and defending champion Wawrinka to grab Centre Court billing and while the Swiss conjured some blazing backhands to whip the noisy crowd into a frenzy, the winners were rare as he surrendered his Roland Garros crown with a 6-4 6-2 4-6 6-2 defeat by the British second seed.

"I knew today if I wanted to win I was going to have to play one of my best claycourt matches. Stan was playing better every match," an emotional Murray, who became the first British man to reach the Paris showpiece since Bunny Austin in 1937, told the crowd with a quivering voice.

"I am extremely proud. I never expected to reach the final here, I always struggled on the clay. I played one of my best claycourt matches today... I hope I can put on a good match on Sunday."


Before that final takes place, Serena Williams will be gunning for her fourth French Open title on Saturday when she takes on the last woman who beat her at Roland Garros -- Spanish fourth seed Garbine Muguruza.

Day 13 of the championships is traditionally men's semi-final day but after one of the wettest weeks on record in Paris, the women were forced to contest their last-four clashes a day later than expected.

Williams seemed listless, bored and completely out of sorts as she finally clipped the wings of flying Dutchwoman Kiki Bertens 7-6(7) 6-4 to reach her 27th grand slam final.

No doubt feeling rather fed up at having to play a third match in as many days, the American appeared to move in super-slow motion between the points, surrendered her opening service games in both sets and sprayed 31 unforced errors long and wide.

None of that stopped the champion from winning though.

"I feel like you have to be still mentally alive, and obviously you need to be physically alive and ready for everything," said the world number one, who will be looking to draw level with Steffi Graf's professional era record of 22 majors.

Muguruza, who like Djokovic was demoted to Suzanne Lenglen Court for her semi, ended the run of 2010 runner-up Samantha Stosur with a no-nonsense 6-2 6-4 win in front of thousands of empty green chairs in the 10,000-seater arena.

The fans, including one dressed as a bizarre green-horned dragon, could not be kept away once Murray and Wawrinka came out for their highly anticipated semi-final.

With Murray having failed to win a set off Wawrinka in any of their previous three battles dating back to 2013, many expected the Swiss third seed to knife Murray's French Open dreams with his wondrous backhands -- just as he had done to Djokovic in the final 12 months ago.

But in front of an audience that included Rod Laver, the last man to hold all four titles at once when he completed the Grand Slam in 1969, Murray heeded his own war cries of "Let's go" to give himself a chance to become the first British man to win the Paris title since Fred Perry in 1935.

Djokovic and Murray, born a week apart in May 1987, are not the only ones in pursuit of records in Paris. Martina Hingis and Leander Paes both completed the full set of grand slam doubles titles when they beat Sania Mirza and Ivan Dodig 4-6 6-4 10-8 (champions tiebreak) in the mixed final.

(Reporting by Pritha Sarkar, editing by John Stonestreet)