NEW YORK (Reuters) - Ivo Karlovic set a U.S. Open record on Tuesday when he banged down 61 aces on his way to a first round victory over Taiwan's Lu Yen-Hsun.

The 37-year-old Croat, who has served the most aces in ATP Tour history with well over 11,000, hit 22 in the second set alone as he outgunned Lu 4-6 7-6(4) 6-7(4) 7-6(5) 7-5 . Tuesday's total beats the previous record of 49 set by the Dutchman, Richard Krajicek, in the quarter-finals in 1999.

"I knew there were a lot of aces because at one stage I was serving one on almost every point but I didn't know it was a record," 21st seed Karlovic told reporters.

Only 10 of the aces came in the final set but Karlovic broke to win the match.

"I'm getting old," he joked.

"I have to work a bit more on my serve, I guess."

(Reporting by Simon Cambers; Editing by Greg Stutchbury)