Andy Murray says he "lost respect" for third seed Stefanos Tsitsipas during a feisty US Open match where the Briton accused his opponent of "cheating" by taking lengthy bathroom breaks.

Tsitsipas, 23, then won the decider for a 2-6 7-6 (9-7) 3-6 6-3 6-4 victory.

"It's not so much leaving the court. It's the amount of time," Murray said. "It's nonsense and he knows it."

The three-time Grand Slam champion added: "That's annoying for me because it sounds like sour grapes because you've lost a match.

"I would have said the same thing if I'd won, I promise."

Tsitsipas, who did not break any rules, also left court for a toilet break at the end of the second set and had a medical time-out for treatment on a foot injury before the fourth set.

"It's just disappointing because I feel it influenced the outcome of the match," Murray said. "I'm not saying I necessarily win that match, for sure, but it had influence on what was happening after those breaks."

During the final set, where Murray was decisively broken in the first game, the 34-year-old Scot could be heard shouting towards his box: "It is cheating."

He also complained to chair umpire Nico Helwerth and US Open match supervisor Gerry Armstrong about the length of time taken by Tsitsipas.

"It's never taken me that long to go to the bathroom ever," Murray told Armstrong.

Tsitsipas said afterwards he has correctly followed the guidelines throughout his career.

Explaining the length of time, the French Open finalist added: "I think it's clear that I took my clothes with me when I left the court.

"That's the amount of time it takes for me to change my clothes and to walk back to the court takes a little bit of time."

Players are allowed two breaks for using the toilet and changing clothes in a five-set match, with breaks only permitted at the end of a set.

"A player may request permission to leave the court for a reasonable time for a toilet break," Grand Slam rules state.

When asked if he could understand Murray's anger, Tsitsipas said: "If there's something that he has to tell me, the two of us should speak to understand what went wrong.

"I don't think I broke any rules. I don't know how my opponent feels when I'm out there playing the match. It's not really my priority."

Murray said long breaks in such a "brutal" match can affect players physically and called for the rules to be changed "because it's not good for the sport, it's not good for TV, it's not good for fans".

"Every single time it was before my serve, as well. Also in the fourth set when I had 0-30, he chose to go and I think he changed his racquet," the former world number one added.

"It can't be coincidence that it's happening at those moments.

"I rate him a lot. I think he's a brilliant player. I think he's great for the game. But I have zero time for that stuff at all, and I lost respect for him."