Two-time Grand Slam champion Stanislas Wawrinka has claimed that it has been harder than last year to adapt to the hot and humid conditions at the US Open in New York.

Many players have been struggling with the heat, but former world number Roger Federer stated yesterday that there is "no excuse" for competitors to retire due to the conditions.

After Wawrinka secured a battling straight-sets victory over Chung Hyeon on Thursday, the Swiss was asked about the conditions.

"I think it's more difficult than last year - more humid, more warm," Wawrinka told reporters. "Today was really tough day with the conditions.

"You have to really be careful how you get ready for the match, what you eat, what you're going to do and what you're going to take during the match. You can see there is many, many players struggling with the conditions today."

Wawrinka will face Ruben Bemelmans in the third round.