The United States star finished the race in 4min 03.57sec at the Rose Bowl Aquatics Centre to better Canadian Philippe Gagnon's previous benchmark of 4:04.20, set on August 7, 2001.

"It's a huge accomplishment to break a world record," said Silverman, holder of four world records including the men's 800m freestyle, the 1500m freestyle and the 400m individual medley.

"I really can't even put it into words what it means to finally get that one.

"I've been close to it before, really close, and I am really happy to start my week with that world record.

"That's the one I wanted.

"That world record has been a monkey on my back since I just missed it in London [2012 Paralympics]."

Silverman was joined on the podium by Alec Elliott of Canada, who touched in at 4:16.61 to take silver, and home athlete Dalton Herendeen, who claimed bronze with 4:20.75.

The day's competition also saw four other world records fall - in the women's 100m butterfly S14 heats thanks to Australian Kayla Clark's time of 1:10.25, the women's 50m freestyle S14 heats when another Australian, Taylor Corry, swam 28.36, in the men's 50m fly final when Brazil's Daniel Dias clocked 33.98 and when Canada achieved 3:54.42 in the 4x100m freestyle 56 point relay.

Daniel Dias clocked a world record breaking 33.98 in the men's 50m fly final ©Getty Images



Elsewhere, the home team ensured it was a clean sweep in both the women's 50m freestyle S9 and S13 races.

Michelle Konkoly topped the S9 podium with a time of 29.40 ahead of team mates Elizabeth Smith and Hannah Aspden, who clocked 30.27 and 30.47, respectively, while the gold went to Martha Ruether with a time of 28.58 in the S13 equivalent, with Becca Meyers placing second in 28.63 and Colleen Young third in 28.80.

"It was awesome to sweep the medals," Konkoly said.

"Before the race, we knew it was possible to sweep with how we've been swimming, so we huddled together and decided to show them what Team USA is made of.

"Lizzie [Smith] had a really great swim and Hannah [Aspden] dropped a tonne of time today.

"It was really, really cool to be there with my team mates next to me."

Other US athletes to win gold on the day included Brad Snyder in the men's 400m freestyle S11 - the event in which he won gold at London 2012 - multiple Paralympic champion Jessica Long in the women's 100m fly S8, Meyers Currie in the women's 100m fly S13 and Cortney Jordan in the women's 50m free S7.

Meanwhile, New Zealand's Paralympic and world champion Mary Fisher entered the competition in fine form to take gold in both the 50m Freestyle S11 and 100m Butterfly S11.

The Pan Pacific Para-Swimming Championships are due to continue until Sunday (August 10).

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