|Venue: Flushing Meadows, New York, Dates: 31 August-13 September|
|Coverage: Live radio and text commentary on selected matches.|
Top seed Novak Djokovic will play defending champion Marin Cilic in the US Open semi-finals on Friday.
Djokovic, 28, beat Spanish 18th seed Feliciano Lopez 6-1 3-6 6-3 7-6 (7-2) in a sweltering New York night session.
The Serb unleashed an angry tirade towards his player box after the second set but finally prevailed at 01:00 local time.
Croatia's Cilic withstood a Jo-Wilfried Tsonga fightback to win 6-4 6-4 3-6 6-7 (3-7) 6-4.
On a sweltering day at Flushing Meadows, Djokovic and Lopez were still suffering in 27C and 66% humidity as midnight came and went.
Djokovic had dominated the opening set but was then furious at dropping the second, thumping his racquet on his bag at the changeover.
The world number one regained control in a lengthy Lopez service game at the start of the third and took a tight fourth in a tie-break after two hours and 39 minutes.
"He's one of the rare players that actually serves volleys on the first and second serve," Djokovic said.
"I'm just glad to get through in four. Obviously, it was frustrating at times but this is quarter-finals of a Grand Slam, this is what you expect."
Champion hangs on in fifth set
Cilic, 26, looked to be on course for a straightforward victory after taking the first two sets, but Frenchman Tsonga was rejuvenated after receiving treatment to his knee.
He fought back to level against the ninth seed, only for Cilic, himself with a strapped-up right ankle, to win in three hours 58 minutes.
The world number nine, who claimed his first Grand Slam title at Flushing Meadows last year, had squandered three match points in the fourth set before allowing 19th seed Tsonga to win a tie-break and take it to a decider.
"That was a big mental fight after that fourth set. It got physical towards the end. It was very hot," Cilic said.
Vinci into new territory
Italian Roberta Vinci, 32, reached her first Grand Slam semi-final by beating France's Kristina Mladenovic 6-3 5-7 6-4.
The world number 43 will face Serena Williams in the last four after the top seed won 6-2 1-6 6-3 against older sister Venus.
Mladenovic struggled with the 34C temperatures on Arthur Ashe Stadium and received treatment in the second set.
The 22-year-old world number 40 had just survived two break points to lead 5-4 before needing treatment from her trainer, who used ice to try and cool her down.
She went on to take the second set, but looked exhausted as Vinci responded to close out the match, with the vital break coming in a 10-deuce game at 3-3.
Quotes of the day
"It's 11:30. To be perfectly honest with you, I don't want to be here. I just want to be in bed right now." Serena Williams reaches her limit when it comes to questions about her sister.
"I will always be the older sister. That's never going to change." Venus Williams can get back to looking out for little sister Serena.
"I was surprised, actually. I don't know. I really don't know why. But, you know, Jo shook my hand, and said, 'Congratulations.' But that was it. I don't know for the rest. If I provoke him or not I have no idea. I hope not." Marin Cilic did not get the warmest of handshakes from Jo-Wilfried Tsonga.
"He just hit the ball a little bit more properly than me at the right moment and that was a huge difference at the end, because he just made it. He just made it." So close but so far for Tsonga against Marin Cilic.
"Well, it's nice. I'm 32. I'm not young." Roberta Vinci on reaching her first Grand Slam semi-final.
"I am proud that I managed, even in very big difficulty and struggle, to not listen to me and stay positive and just try to fight till the end." Kristina Mladenovic won the battle with herself, if not Vinci.