Roger Federer is on course for 20th Grand Slam win after his clinical performance against Spain’s Feliciano Lopez, defeating him in straight sets to reach the fourth round.

The 36-year-old Swiss hasn't really hit the ground running in the US Open, requiring five-sets in the first two rounds but showed class against the Spaniard, beating him 6-3, 6-3, and 7-5 as the match lasted for just one hour and 46 minutes under a closed roof at the Arthur Ashe Stadium.

Five-time champion Federer faces Lopez boasting a 12-0 record over the 31st seed.

"I'm really excited how I feel after two five-setters," the 19-time Grand Slam champion said.

"It was clearly nice to go up two sets to love for a change. Feels different from there."

While top seed Rafael Nadal overcame tough and stubborn resistance from Argentina’s Leonardo Mayer to reach the fourth round at the Flushing Meadows. The 31-year-old lost the first set but the Spaniard fought back to win 6-7 (3-7) 6-3 6-1 6-4 after three hours and 16 minutes.

Nadal has been in sync since the start of the tournament but this match tested the World No.1 as Nadal saw 13 break points go begging before finally breaking the 59 ranked after nearly two hours of battle.

"All the matches have been very tight - I am very happy," said Nadal.

"I don't know how many break points I had before I got the first one. Mentally, I fought a lot until that moment, and then I think I played better."

Rafael Nadal will face Ukraine’s Alexandr Dolgopolov in the round of sixteen.