Sinner edged the opening two sets on tiebreaks under the closed roof but was rocked on his heels by a Berrettini fightback before prevailing 7-6(3), 7-6(4), 2-6, 7-6(4).

Berrettini, who was runner-up to Novak Djokovic in 2021 but was plagued by injuries last year and is now ranked down at 59th, looked capable of dragging the match into a decider with some heavy-metal tennis.

Top seed Sinner was wobbling when some scrappy groundstroke errors meant he went a break down early in the fourth set, but he managed to wrestle back control in the nick of time.

Berrettini saved a match point when serving at 5-6 in the fourth set and belted away a forehand to set up the third tiebreak of an absorbing tussle.

The law of averages suggested the big-serving Berrettini would come out on top this time but once again Sinner was as cool as a cucumber when it mattered to get the job done shortly before Wimbledon's 11pm curfew.

"It was very tough to face Matteo in the second round in such an important tournament," Sinner, who embraced his friend and compatriot warmly at the net, said on court.

"Today was a high-level match and we both played well and in the three tiebreaks, I got a bit lucky. I knew I had to raise my game a level today, he is a grasscourt specialist.

"There were some ups and downs which is normal but I'm happy to be in the next round."

Sinner, who extended his record against fellow Italians to 14-0, will continue his quest to add the Wimbledon title to this year's Australian Open against Serbia's Miomir Kecmanovic on Friday.