Lilly King broke the women's 50m breaststroke world record in seeing off rival Yuliya Efimova on Sunday, with the Russian insisting the war-of-words between the pair is now over.

King clocked 29.40 seconds in Sunday's 50m final at the world championships, breaking the four-year-old record, with Efimova taking silver at 0.17 back.

This was the second world record the 20-year-old King has broken in Budapest after also lowering Ruta Meilutyte's time for the 100m breaststroke in winning Tuesday's final.

The victory was King's second of week over Efimova, who took bronze in the 100m final but had beaten the American over 200m with a commanding display on Friday when King finished fourth.

King sparked a war of words at last year's Rio de Janeiro Olympics when she branded the Russian a drugs cheat after Efimova's 16-month ban for doping, which ended in February 2015.

The Russian responded by saying King had turned Olympic swimming into war, but Efimova insisted peace has now broken out between the pair in Budapest.

"What happened before, in another competition, it doesn't matter now," said Efimova.

"I'm really happy and today she (King) told me she loves to race with me, because it makes her race faster too and it makes it more interesting to watch."

The 25-year-old Russian was blunt about her doping past after being caught taking a hormone steroid which led to her 16-month ban.

"Sometimes people make mistakes, it's an old question, like when you're driving and you're speeding just a little bit high," said Efimova.

"It's not like you can die or something, it's just like next time I will do things right.

"Sometimes shit happens and you can do nothing, people should have a second chance."

Efimova said she is "not best friends, but good friends" with King and although the American was quick to clairfy, she agreed their relationship has improved on Rio.

"Obviously, we are not best friends, we are rivals, but I was having a good time racing her," said King.

"We have definitely been a lot more civil than we were last year, so I'm enjoying that.

"I offered most of my opinions on (doping) last year and I'd rather just talk about the races.

"I'm feeling pretty good, five races, four world records, pretty happy with that," she added, after setting two individual breaststroke records, plus mixed and medley relay records.

"The relay records were the cherry on top, but the individual records are definitely things I had been looking forward to."

Source: AFP