Gwangju - American Caeleb Dressel said on Friday he was not aiming to top the remarkable seven world titles he bagged two years ago, but was focused on overcoming rival Kyle Chalmers in the 100m freestyle in Gwangju.

Dressel, US swimming's new golden boy, took home seven golds in Budapest, but will face fierce competition in the men's blue riband race from Olympic champion Chalmers.

Chalmers is in blistering form after clocking 47.35 in qualification - almost half a second quicker than his winning time in the 2016 Rio final.

"I'm not super worried about counting medals or just because I got seven last time, it means I have to do eight. It's really just about getting my hand on the wall first," Dressel said.

"He (Chalmers) is a great competitor, I look forward to racing him, he swims a smart 100m freestyle," he added, describing the Australian as "a good friend".

Despite pipping Dressel to the 100m freestyle title at the Pan Pacific championships last year, Chalmers described himself as the underdog in Gwangju and said he was happy for all eyes to be on the US swimmer.

"The more pressure the Americans put on him, the better. It doesn't really worry me," the 21-year-old told Australian media.

"To me, he's just another swimmer. I don't really take in who my competitors are or been hugely involved in swimming in that regard."

Both swimmers will have one eye on Brazilian Cesar Cielo's 10-year-old world record of 46.91.

But 22-year-old Dressel appeared relaxed and confident on Friday, saying "there's really positive vibes going around everybody".

"I'm around good friends and I do enjoy these champs a lot. I've got cards and plenty of other distractions."

Asked whether he could surpass Cielo's record, he said: "I don't know, there's a lot of other factors that are out of my control. I'm going to swim the smartest race that I can but I'm not in control of the times that show up on the scoreboard."

Much to his dislike, Dressel has drawn lofty comparisons with US swim legend Michael Phelps after he matched his compatriot's record seven golds in Budapest - becoming only the second swimmer to do so at a single long course world championships.

And despite losing out in the freestyle at the Pan Pacifics, he secured victory in the 100m butterfly, powering to victory in a tournament-best 50.75.

Dressel's mind was also on a possible relay spot as the American team battle it out for the four places.

"For me it is a big spot to fill because growing up and watching some of the studs that were on some of these crazy relays (in Beijing and London)," he said.

"What a privilege to be in that spot and you do want to be part of that history that the USA has been so dominant with."