Fina World Championships
Date: 17 July-2 August (swimming from 26 July) Venue: Rome
Live/highlights on BBC Two, Red Button and BBC Sport website
Cavic v Phelps is one of the most eagerly anticipated events in Rome
Milorad Cavic smashed Michael Phelps' world record en route to Saturday's final of the 100m butterfly at the World Swimming Championships in Rome.
Phelps beat Cavic by a hundredth of a second at last year's Beijing Olympics to stay on course for his record haul of eight gold medals.
But Serbia's Cavic upstaged Phelps by clocking 50.01 seconds in his semi-final, while Phelps won his in 50.48.
Phelps set the previous mark of 50.22 at the US nationals on 9 July.
Britain's Michael Rock failed to reach the final, finishing 13th in 51.41 to lower the British record he set in the morning session.
"I didn't want to go out so fast, but I had so much energy in my body that I couldn't help it," said Cavic. "I'm capable of swimming under 50, which would be enough to win the gold."
The third option would actually be a dream of mine, to have the whole final everybody swimming in briefs
Despite the defeat in Beijing, Cavic is still convinced he is the faster swimmer and even offered to buy Phelps a new 100% polyurethane suit in Rome to make sure there is no controversy over the type of garment worn.
Phelps is contracted to Speedo and is remaining loyal to their outdated LZR suit which is only 50% polyurethane, but the Arena X-Glide, worn by Cavic, and a similar suit by Jaked are considered the fastest at these championships, where 29 world records were set over the first five days.
"If Mike wants an Arena, he just has to say it," Cavic said after the heats on Thursday morning.
"If he wants a Jaked and they don't want to give it to him free, I'll buy it for him. He has options. I think in the media it's been portrayed that he has no option, he has to swim for (Speedo). It's a complete lie."
Fina, swimming's governing body, will ban all hi-tech suits from 1 January 2010 after 35 world records were set in the first six days in Rome.
Cavic added: "I think there's three options for Michael.
"The first option is to use the suit that he's wearing, the second option is to get one of these (polyurethane) suits, which I guarantee Arena will provide him within the hour, as soon as he wants.
"The third option would actually be a dream of mine, to have the whole final everybody swimming in briefs. I swear to God, this is it, this is what I want, but this is the most unrealistic of all scenarios."
Phelps, who retained his 200 butterfly crown on Wednesday with a world record, refused to comment but his coach Bob Bowman shrugged off Cavic.
"He's a very good swimmer, a super-talented swimmer and he's free to say whatever he wants," Bowman said. "We know that Michael usually lets his swimming do his talking, and we'll know by (Saturday) night what the deal is."