NEW YORK (AFP) - Ivo Karlovic served his way into the US Open record books on Tuesday when he fired 61 aces in his 4-6, 7-6 (7/4), 6-7 (4/7), 7-6 (7/5), 7-5 win over Lu Yen-Hsun of Taiwan.

Karlovic, 37, beat the previous best of 49 aces for one match in New York served up by Richard Krajicek in his quarter-final loss to Yevgeny Kafelnikov in 1999.

"I knew there were a lot of aces because there was a period (in the second set) when almost every serve was an ace. I knew there was a lot but I didn't know it was this many," said the 2.11m- tall Karlovic.

He had three times previously served more than 50 aces in a tournament - his previous best in a tour match was 55 against Lleyton Hewitt in 2009 at the French Open.

In the same year, he served 78 aces against the Czech Republic's Radek Stepanek in a Davis Cup clash.

He has now served 11,277 aces in his career, 1,000 more than second-placed Goran Ivanisevic.

"Of course this is my best shot. I have worked a lot on it. I'm proud of it," said Karlovic.

America's John Isner holds the all-time Grand Slam record of 113 aces served during his famous 70-68 fifth-set victory over Nicolas Mahut in the first round of Wimbledon in 2010.

Karlovic's achievement on Tuesday sparked an immediate Twitter reaction.

"@ivokarlovic dude 61 WTF," tweeted Australian star Nick Kyrgios.

Karlovic replied, tongue in cheek: "Yeah got some shoulder issues!"