* Rallies from two-sets-to-one deficit
* Faces either Nadal or Gasquet for title (Adds quotes, details)
By Will Swanton
NEW YORK, Sept 7 (Reuters) - Top seed Novak Djokovic won a five-set thriller against Switzerland's Stanislas Wawrinka in the semi-finals of the U.S. Open on Saturday.
Djokovic recovered from a two-sets-to-one deficit to beat Wawrinka 2-6 7-6(4) 3-6 6-3 6-4 in front of a packed house on Arthur Ashe Stadium at Flushing Meadows.
"These matches are what we live for, what we practice for," Djokovic said. "I want to congratulate my opponent, he played a great match."
The Serb's supreme fitness levels were crucial as the ninth-seeded Wawrinka became fatigued during the final two sets.
"Stan played aggressive. He played the better tennis. I was just trying to hang in there. I was fortunate to play my best tennis when I needed to," Djokovic added.
An incredible 21-minute, 30-point game at 1-1 in the fifth set went Wawrinka's way, but he dropped serve at 2-2 as Djokovic assumed control.
Wawrinka cracked 57 winners to Djokovic's 38 but a first-serve percentage of 50 proved costly for the Swiss.
Djokovic served out the match to 15 to win in four hours and nine minutes.
Djokovic will clash with either Spain's second-seeded Rafa Nadal or eighth-seeded Frenchman Richard Gasquet in Monday's final.
"It was a great tournament for me," Wawrinka said. "Tough match, tough loss. I gave everything. I fought until the end. With this crowd, it was an amazing experience."
Wawrinka played the more aggressive tennis from the outset, holding a service break in the second set before Djokovic's comeback began.
The Serb received a caution for illegal courtside coaching at 2-4. Clearly displeased, he broke Wawrinka's next service game and went on to control the tiebreaker.
The final set took an hour and three minutes before Djokovic and Wawrinka embraced at the net.
Both players earlier had raised their arms to the crowd after the 21-minute game, resulting in a loud standing ovation.
Djokovic had five break points in that game, without being able to convert. He held his service quickly, and broke Wawrinka to lead 3-2 in the decisive break.
"I guess everyone was thinking whoever wins this game, wins the match," Djokovic said. "I told myself I was going to have to fight again."
(Reporting by Will Swanton, Editing by Gene Cherry)