Former world number one Novak Djokovic was relieved to make it through to the second round of the US Open after feeling the heat in brutal conditions in New York.

Another day of stifling heat and humidity wreaked havoc at Flushing Meadows, where 13-time grand slam champion Djokovic survived 6-3 3-6 6-4 6-0 against Marton Fucsovics on Tuesday.

The heat rule was implemented as sixth seed Djokovic and Hungary's Fucsovics struggled in the scorching conditions on Arthur Ashe Stadium.

Djokovic – who required a visit from the doctor and trainer during the second set – and Fucsovics were granted a 10-minute break before the fourth set.

Speaking to reporters afterwards, two-time US Open winner Djokovic said: "It was a tough one. We both struggled. We were not the only ones today. Obviously you had almost 10 retirements in the men's draw. Brutal conditions.

"But it is what it is. You have to kind of deal with it. I had to find a way to dig myself out of the trouble. It was a set all and I was break down. I think that was a turning point, 4-3 in the third when he was serving, I managed to play a good game.

"I saw that he's starting to slow down a bit. He started to experience some physical issues. That's where I felt, well, this is the time to use this kind of opportunity and try and get back in the match.

"After that, I haven't lost a game till the end of the match. Obviously a 10-minute break was something that was very much appreciated and needed. I'm glad that we had that. Obviously, I haven't experienced that before. That was the first time. I think we both needed it."

"I thought the 10-minute break was great," Djokovic continued. "I thought it was, as I said, a much-needed break for both of us after playing two and a half hours, struggling. To be able to go back in the locker room and change clothes, take shower, grab something to eat, whatever, and just refresh, be in the shade, be in a cooler room, and then go out, it's quite different. You feel refreshed."

Djokovic faced a break point to go down 4-1 in the third set but he refused to surrender in the difficult conditions, adding: "I did not think I would not finish it. I was obviously hoping and praying that I'll get to feel better as the match progresses. I felt better, especially after that 10-minute break. For the first three sets, it was a survival mode for both of us.

"You have those days, you have those matches where you just have to figure out a way to hang in there, deal with these particular circumstances."