ROME: Milorad Cavic made a sensational statement in the World Championships 100m butterfly semi-finals on Friday, breaking Michael Phelps’s world record and nearly smashing the 50-second barrier.

Now the Serbian takes the upper hand into his grudge match against Phelps, where he’ll try to balance the scales after Phelps out-touched him by one one-hundredth of a second in the Beijing Olympic final.

Cavic won the second semis in 50.01sec to break the world record of 50.22 that Phelps had set at the US Championships on July 9.

It was one of six world records on the night, taking the total to a whopping 35 with two days still to go. The flood has been fueled by polyurethane swimsuits such as the Arena X-Glide worn by Cavic. Amid complaints that the suits are artificially re-writing the sport’s history, FINA announced on Friday that they would indeed implement the planned ban on January 1, rather than waiting until later next year.

In the meantime, it remained open season on records in Rome. Three of the five titles on offer were won in world record times — Aaron Peirsol in the men’s 200m backstroke, Britta Steffen in the women’s 100m freestyle and the United States in the men’s 4x200m freestyle relay. The only exceptions were the men’s and women’s 200m breaststroke finals — and the world record had been broken in both a day before.

Women butterfliers delivered another record two-for-one as first Marleen Veldhuis with a time of 25.28 and then Therese Alshammar in 25.07 lowered the 50m fly mark in the semis. Peirsol bounced back from his failure to make the 100m back final by crushing his own 200m back world record in 1:51.92.

Until Friday, Japan’s Ryosuke Irie had been the only swimmer to break 1:53, but his 1:52.86 set in Canberra this year was never ratified because he was wearing an unapproved suit. That meant Peirsol, who also wears an X-Glide, lopped 1.16sec off his world standard of 1:53.08.

Germany’s Olympic champion Britta Steffen won the women’s 100m freestyle, lowering her own world record for the second time at these championships with a time of 52.07sec. Defending world champion Libby Trickett of Australia led at the turn, but was overtaken by both Steffen and 19-year-old Briton Fran Halsall, who took silver in 52.87 as Trickett made do with bronze in 52.93.

The US team of Phelps, Ricky Berens, David Walters and Lochte shaved one-hundredth of a second off the world record set by America’s gold medal-winning 4x200m free relay team in Beijing, lifting the world title in 6:58.55 ahead of Russia (6:59.15) and Australia (7:01.65).