BUDAPEST — Katie Ledecky earned a second gold medal Sunday at the World Aquatics Championships here by helping the United States win the women’s 4x100m freestyle final.

Sweden’s Sarah Sjostrom had set a world record of 51.71sec in the opening leg, becoming the first woman to break the 52-second barrier.

The US clocked three minutes, 31.72 seconds with Australia taking silver at 0.29secs back, while the Netherlands earned bronze at 0.92.

Ledecky finished the opening day of the world champs with two golds after her victory in the women’s 400m freestyle final earlier at the Duna Arena.

The US was third midway through Ledecky’s leg, but the 20-year-old blasted through the final 50 meters to give her team the lead.

She handed over to Simone Manuel, the joint 100m freestyle champion at the 2016 Olympics, who touched the wall just ahead of Australia’s Emma McKeon.

Sjostrom’s Sweden finished fifth despite a sensational opening 100 meters, beating the previous record of 52.06sec set by Australia’s Cate Campbell in 2016.

That is the biggest world record improvement in this event since Libby Trickett of Australia beat Britta Steffen’s mark by 0.42 in 2008.

Ledecky claimed her first gold medal, cruising to a dominating win in the 400m freestyle though she failed to break her own world record.

As expected, the 20-year-old American pulled away on the very first lap and was essentially racing the clock the rest of the way. She finished in 3 minutes, 58.34 seconds — more than 3 seconds ahead of U.S. teammate Leah Smith. China’s Li Bingjie took the bronze.

In the first swimming final of the championships, China’s Sun Yang got a bit of payback for his Olympic defeat in the men’s 400 freestyle by pulling away from rival Mack Horton of Australia.

Yang was in a league of his own in a stacked field that featured the past three Olympic champions: Horton (2016), Sun (2012) and South Korea’s Park Tae-hwan (2008).

“I have no exact target for the week,” the 25-year-old Sun said through an interpreter.

The Chinese star finished more than two body lengths ahead of the field, touching the wall in 3:41.38. Horton settled for the silver, far back at 3:43.85, while Park finished fourth behind bronze medalist Gabriele Detti of Italy.

Last summer in Rio de Janeiro, Horton defeated Sun in the 400 free final after calling him a “drug cheat” over his three-month doping suspension in 2014. The Aussie has made it clear he doesn’t think anyone who tests positive should be allowed to compete — which also applies to Park, who served a doping suspension that ended before the 2016 Olympics. — Agencies