Carlos Alcaraz stayed firmly on course to defend his US Open title Monday as he reached the quarter-finals with a straight-sets win over Italy's Matteo Arnaldi.

Alcaraz eased past the 61st-ranked Arnaldi 6-3, 6-3, 6-4 under the roof on Arthur Ashe Stadium and will face sixth seed Jannik Sinner or 2020 runner-up Alexander Zverev for a place in the semi-finals.

The Spaniard beat Sinner in five sets in last year's quarter-finals in New York in a match which set a record for the latest ever finish at the tournament of 2:50am.

"Everybody knows about the last match against Jannik, it could be a great quarter-final but let's see who I'm going to play."

"Sascha (Zverev) is playing really well and Jannik as well."

Alcaraz, 20, is the first man to make the last eight or better in his first three US Open appearances since 1980. 

He broke midway through the opening set and then twice in the second, stylishly charging into a two-set lead with a delicate forehand on the run past an outstretched Arnaldi.

Arnaldi pounced on his first opportunity to break Alcaraz early in the third set only to see his advantage erased the following game.

Alcaraz ripped a sensational cross-court forehand to bring up three match points on Arnaldi's serve at 4-5 and closed out victory inside two hours.

"I think the intensity from the beginning until the last ball, I played a really solid match, less mistakes," said Alcaraz.

"I'm really happy with the performance in general."

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