World number one Rafael Nadal overcame a shaky start to comfortably beat Dusan Lajovic in round one of the US Open on Tuesday.

Nadal - the champion at Flushing Meadows in 2010 and 2013 - faced early pressure under the roof of Arthur Ashe Stadium as his opponent came out firing.

However, Lajovic was unable to maintain his initial level of performance and the underdog's hopes of victory swiftly evaporated after he had been broken to love serving for the opening set.

There was a sense of inevitability thereafter as Nadal charged to a 7-6 (8-6) 6-2 6-2 victory, maintaining his unbeaten record in first-round matches at Flushing Meadows.

Luck was on Lajovic's side in the opening exchanges as he benefited from more than one fortuitous bounce off the net cord, but there were also plenty of quality strokes from the Serbian, who is ranked 85th in the world.

Swinging freely, Lajovic claimed an early break and retained his lead until the 10th game, when the pressure of the occasion seemed to get to him.

Nadal was still made to work hard to move in front via a tie-break, yet he was soon in command as he reeled off the first three games of set two, breaking Lajovic twice.

Although a sloppy service game briefly stunted the top seed's momentum, Lajovic never looked likely to find a way back into the contest.

The crowd was briefly roused when Nadal fell 15-40 down serving with a 2-1 lead in the third set, but Lajovic was unable to convert three break points and the end was not long in coming.

Nadal will face Taro Daniel or Tommy Paul in round two.

STATISTICAL BREAKDOWN

Nadal [1] bt Lajovic 7-6 (8-6) 6-2 6-2

WINNERS/UNFORCED ERRORS
Nadal - 33/34
Lajovic - 14/39

ACES/DOUBLE FAULTS
Nadal - 5/5
Lajovic - 1/2

BREAK POINTS WON
Nadal - 6/11
Lajovic - 2/8

FIRST SERVE PERCENTAGE
Nadal - 62
Lajovic - 72

PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Nadal - 67/59
Lajovic - 54/52

TOTAL POINTS
Nadal - 105
Lajovic - 83