Defending champion Marin Cilic was the first man to qualify for the quarter-finals of the US Open, beating Jeremy Chardy.

The ninth seed from Croatia was taken to five sets by Mikhail Kukushkin in the third round, but was not hampered by fatigue as he beat Chardy 6-3 2-6 7-6 (7-2) 6-1 at Arthur Ashe Stadium on Sunday.

Cilic made 53 unforced errors against Kukushkin, but cut that down to 23 and came up with 52 winners.

The Cilic serve proved to be a major weapon as he fired down 23 aces, while Chardy, who beat seventh seed David Ferrer in the third round, missed out on a second grand slam quarter-final of his career.

Cilic's win ensured he will face another Frenchman in the form of Jo-Wilfried Tsonga in the last eight at Flushing Meadows. 

Tsonga accounted for countryman Benoit Paire 6-4 6-3 6-4 in one hour, 42 minutes on Louis Armstrong Stadium.

The world number 18 - with a 20-10 win-loss record on tour this year - capitalised on Paire's 35 unforced errors as he won through to his second US Open quarter-final.

Spaniard Feliciano Lopez also progressed via a 6-3 7-6 (7-5) 6-1 win over Fabio Fognini in New York.

Fognini conquered Rafael Nadal in the third round but the Italian was no match for Lopez, who reached his maiden quarter-final at Flushing Meadows.

Lopez will meet either world number one Novak Djokovic or Roberto Bautista Agut in the next round.