Defending champion Marin Cilic reached the US Open semi-finals on Tuesday with a 6-4, 6-4, 3 -6, 6-7 (3/7), 6-4 win over France's Jo-Wilfried Tsonga.
Croatian ninth seed Cilic goes on to face Serbian top seed Novak Djokovic for a place in Sunday's final.
Over a four-hour battle on Arthur Ashe Stadium, the 26- year-old claimed a fifth win in six matches against Tsonga, firing 29 aces and 63 winners.
But the 30-year-old Tsonga made him work in 35-degree (95 F) heat, saving four match points before the champion went through.
"It was a big mental battle. I lost the fourth set despite having three match points. Jo played some amazing shots," said Cilic. "It was very hot, very demanding. I am proud that I stuck to my game plan and didn't back down."
It was the Frenchman who cracked first, his perfect serving run ending at 60 as Cilic converted on a fourth break point for a 5-4 lead on his way to securing the opener.
Cilic turned the screw again in the second set, breaking for 3-2 courtesy of a fifth double fault by Tsonga.
Tsongo won three games on the bounce to claim the third set.
Tsonga fought off two match points in the 10th game of the fourth set and another in the 12th. The 30-year-old capitalised on his escape, sweeping the tie-breaker.
But Cilic finished the fresher, breaking for a 3-2 lead and secured the victory when Tsonga fired a forehand wide.
Novak Djokovic defeated Feliciano lopez 6-1, 3-6, 6-3, 7-6 (7/2) to reach the US Open semi- finals, a 21st last-four spot in his last 22 Grand Slams.
The top seed and 2011 champion, claimed his 55th match win in New York.
The 33-year-old lopez, playing in his first US Open quarter-final, was shellshocked in the first set.
lopez managed just five points on the Djokovic serve in the 25-minute opener and was broken twice.
But lopez rallied in the second set, breaking in the second game on his way to a 4-1 lead.
Djokovic saved one set point but a 10th ace gave lopez the set 6-3.
The Serb, bidding for a 10th Grand Slam title in New York, took the only break of the third set off a lopez double fault in the second game.
He then played the perfect tie-breaker in the fourth to take victory while lopez was left to rue his 48 unforced errors.
Djokovic will take a staggering 13-0 career record over defending champion Marin Cilic into their Friday semi-final.