Daniil Medvedev reached the US Open semi-finals after beating Andrey Rublev in hot and humid conditions that he said would cause a player to "die".

"One player is going to die and you are going to see," he said into a camera during the match in New York.

Medvedev won his only Grand Slam at the US Open in 2021 after beating Novak Djokovic in the final.

His semi-final on Friday will be against Spain's defending champion Carlos Alcaraz or Alexander Zverev of Germany, who play in Wednesday's night session.

World number eight Rublev has now failed to make the semi-finals of a major in nine attempts.

'It was brutal'

With a heatwave sweeping over New York, the match was played under a partially closed roof on the hottest day of the tournament so far, with temperatures expected to rise to 35C on Wednesday.

Both players looked physically and emotionally drained as Medvedev eventually wrapped up the match after two hours and 48 minutes before comparing the "brutal" conditions to the weather he experienced during the 2020 Tokyo Olympics.

"The only good thing I see in these conditions is that both [players] suffer. It's tough for both of us," he said in his on-court interview.

Medvedev and Rublev each took lengthy bathroom breaks in between sets for a moment of respite from the heat and to change their sweat-drenched clothes.

The pair also hosed themselves down with cold water, sat under ice towels and made the most of the air conditioning units at their seats.

"At the end of the first set I couldn't see the ball anymore. I played with sensations - try to go for it, try to run, try to catch the balls - and he did the same sometimes," Medvedev added.

"A few moments in the third set he was up a break. I couldn't wait to go to the cold shower, but the thing about that is when you come out either you can't move because your body blocks or you feel better."

Medvedev beats best friend to reach semi-finals

While Medvedev has made it to four Grand Slam finals, winning one, Rublev - who broke into the world's top 10 in October 2020 - is still bidding for a first major semi-final.

The pair have been best friends since the age of six and Rublev is godfather to Medvedev's daughter, with the 2021 champion calling him "family" before their last-eight encounter on Arthur Ashe Stadium.

Rublev found himself a break up at the start of every set, but Medvedev was able to find a shift in momentum each time despite taking two medical timeouts and using an inhaler as he struggled with his breathing.

The higher-ranked Russian got the key break for 5-4 to serve out the opening set and after being 3-1 down in the second, he won five successive games and left Rublev looking dejected.

With the finish line in sight, and after letting four match points come and go on Rublev's serve, Medvedev wrapped up the victory on the fifth as his opponent fired a forehand into the net.

"I know he never gives up. The thing is he knows I never [give up] too," Medvedev said.

Despite the hard court being his preferred surface, Medvedev struggled in the run-up to the US Open, suffering a quarter-final exit at the hands of Australia's Alex de Minaur in Canada before losing in the second round of the Cincinnati Open to Zverev.

However, he has found his form in New York, dropping just two sets en route to the semi-finals.