British number one Dan Evans overcame hot conditions and a gutsy opponent in Brazil's Thiago Monteiro to reach the US Open second round.

Heather Watson and Harriet Dart both lost on day one at Flushing Meadows.

Watson, 29, was beaten 6-1 6-4 by Slovenia's Kaja Juvan, while qualifier Dart lost 6-7 (6-8) 6-4 6-2 to France's Caroline Garcia.

Watson, set to become Britain's top-ranked women's player following Johanna Konta's withdrawal, has now lost all 10 of her first-round matches in New York.

Dart, 25, played excellently in the first set but trailed by a break in the second set when she had to go off court for further treatment on what appeared to be a left leg injury.

After a long delay, she was unable to regain the upper hand against former world number four Garcia and missed out on a place in the second round for the first time.

The pair were among six British players due to play on Monday's opening day of the final major of the 2021 season.

But that number was reduced when Konta pulled out of her first-round match against France's Kristina Mladenovic with a thigh injury.

Evans through in 'brutal' New York conditions

Evans, 31, was the first British player on court and ensured he started the nation's singles challenge on a positive note.

After missing the Olympics because he contracted Covid-19, Evans had lost four of his five matches since Wimbledon and looked to be waning physically as Monteiro levelled at one set all.

During the second set Evans needed ice packs and then also had treatment on his foot after winning the third set.

Former British number one Tim Henman, working at Flushing Meadows as a television commentator, described playing in the heat and humidity as "brutal".

But Evans dug deep physically and raced to 4-0 up in the fourth set before completing victory.

The Briton will play American world number 64 Marcos Giron in the second round.