* Top seed Djokovic overcomes Wawrinka in five sets
* Nadal strolls through in straight sets win over Gasquet
* Czechs Hlavackova and Hradecka win women's doubles final (repeats fixing score in first set of women's doubles final in third-last para)
By Larry Fine
NEW YORK, Sept 7 (Reuters) - World number one Novak Djokovic and number two Rafa Nadal set up a mouthwatering men's singles final at the U.S. Open with victories in the semi-finals at Flushing Meadows on Saturday.
Monday's U.S. Open championship showdown will be the third in four years for Djokovic and Nadal at the U.S. National Tennis Center after they advanced in contrasting fashion.
Top seed Djokovic sealed his berth first by overtaking gutsy ninth seed Stanislas Wawrinka of Switzerland in a heart-pounding 2-6 7-6(4) 3-6 6-3 6-4 victory over four hours.
Nadal conserved his energy, dismissing eighth-seeded Richard Gasquet 6-4 7-6(1) 6-2 to improve his career record to 11-0 against the Frenchman and his 2013 hardcourt record to 21-0.
The Spaniard, winner of 12 grand slam titles, won his only U.S. Open crown in 2010 against Djokovic, who claimed his Flushing Meadows title the following year against Nadal. Last year Djokovic was runnerup to Briton Andy Murray.
"Last year I didn't have the chance to play on this court," said Nadal, who was sidelined seven months due to a knee injury.
"To have the chance to play in the final Monday is just a dream for me. It has been two amazing weeks for me."
Djokovic and Nadal are the most familiar of rivals and will be playing against each other for a tour record 37th time. Nadal leads their series 21-15.
"Novak is an amazing competitor," said the reigning French Open champion. "His results say he is probably one of the best players I have ever seen. He's a great champion and will be a tough final for me, but I hope to be ready for that."
While Nadal took apart Gasquet in his semi-final, Djokovic got off to a slow start against an inspired Wawrinka and relied on his stamina to wear down the Swiss.
The tumultuous match included a warning for courtside coaching from Djokovic's box, the mangling of a racket by a frustrated Wawrinka and a medical timeout for the Swiss for a strained thigh muscle.
It reached a crescendo at 1-1 in the fifth set on Wawrinka's serve.
The combatants locked into a marathon duel that lasted 21 minutes and featured a series of fierce rallies and brilliant shot-making.
Wawrinka fought off five break points among 12 deuces before closing out the game on the 30th point with a service winner, and players earned warm ovations for their desire and skill.
"These matches are what we live for, what we practise for," Djokovic said after reaching his fourth successive U.S. Open final.
"All the credit to (Wawrinka) for being so aggressive and playing so well. I'm just fortunate to play my best tennis when I needed to."
Djokovic said he had to regroup after that epic game.
"Twenty-one minutes. Wow," said the Serb. "I was thinking whoever wins this game is going to win the match. I told myself I was going to have to fight again."
The Herculean effort seemed to sap the last bit of energy from Wawrinka, who had earlier left the court for treatment of a thigh strain during the changeover when trailing 4-1 in the fourth set.
Djokovic held serve, then broke Wawrinka in the next game for a 3-2 lead and served out to win another classic encounter between the pair following their five-set struggle in the fourth round of the Australian Open, where the Serb closed out the decisive set 12-10.
"It was a great tournament for me," said Wawrinka after his first grand slam semi-final. "Tough match, tough loss. I gave everything. I fought until the end. With this crowd, it was an amazing experience."
Czech pair Andrea Hlavackova and Lucie Hradecka capped off Saturday's programme by winning the women's doubles title with a 6-7(4) 6-1 6-4 win over Australians Ashleigh Barty and Casey Dellacqua.
World number one Serena Williams will take on number two Victoria Azarenka for the women's singles title on Sunday in a tantalising rematch of last year's championship decider.
That will follow the men's doubles final with Austria's Alexander Peya and Brazilian Bruno Soares facing Radek Stepanek of the Czech Republic and India's Leander Paes.
(Editing by Gene Cherry / Ian Ransom)