SCOTTISH tennis star Andy Murray has fired a dig at his US Open opponent Stefanos Tsitipas for his lengthy toilet break.

The first-round clash between Murray and Tsitipas of the major tennis tournament last night lasted for nearly five hours but saw the Scot lose out to the number three seed.

Before the decisive fifth set, Tsitipas left the court for seven minutes as Murray was left to wonder what the Greek was doing.

READ MORE: Andy Murray rolls back the years in five-set thriller at US Open

Murray complained to the umpire and match supervisor Jerry Armstrong and was heard to ask the official: "The toilet’s right there. What’s he doing in there?

“It’s never once taken me that long to go to the toilet, ever.”

The Scot has since taken aim at his Greek opponent again today with a cheeky tweet.

Murray wrote: "Fact of the day. It takes Stefanos Tsitipas twice as long to go the bathroom as it takes Jeff [Bezos] to fly into space. Interesting."

Murray said after the match that the delay "influenced the outcome" due to the amount of time of stopped play "affects you physically".

He added: "I’m not saying I win that match for sure, but it had influence on what was happening after those breaks.”

Tsitsipas left the court for a toilet break before the third set and also received medical treatment for a foot injury before the fourth set.

Former Wimbledon champion and Olympic gold medalist Murray did say that Tsitsipas was a "brilliant player" and "great for the game", but added that he had "lost respect" for the Greek.

Murray said: "I have zero time for that stuff, at all, and I lost respect for him. If everyone else feels like that’s totally cool and there’s no issue with it then maybe I’m the one being unreasonable. But I think it’s nonsense and he knows it as well.”

Tsitsipas will meet Adrian Mannarino of France in the second round tomorrow.