Mack Horton and Swimming Australia will receive an official warning letter as the Aussie Olympian and his Chinese arch rival prepare to hit the pool again on Tuesday.

All eyes will be on Horton and China’s mega-star world champion Sun Yang when they compete in Tuesday’s 800m freestyle heats at the world swimming titles.

Horton sparked international furore when he staged a bold podium protest, refusing to stand next to or shake Sun’s hand when the Chinese athlete took gold in the 400m freestyle final on Sunday.

Swimming Australia had been confident Horton, who was relegated to a silver medal, would escape sanction.

However FINA has confirmed not only Horton but also the national body would receive a warning letter despite SA claiming it had no prior knowledge of the silent protest.

“The FINA executive met today in Gwangju to analyse the situation related with the men’s 400m free victory ceremony and has decided to send a warning letter to Swimming Australia and to Mack Horton,” the FINA statement said.

“While FINA respects the principle of freedom of speech, it has to be conducted in the right context.

“As in all major sports organisations, our athletes and their entourages are aware of their responsibilities to respect FINA regulations and not use FINA events to make personal statements or gestures.

“The matter over which Mack Horton was allegedly protesting is currently under review by CAS and therefore it is not appropriate for FINA to prejudice this hearing by commenting further.”

Silver medalist Mack Horton did not mount the podium next to gold medalist Sun Yang, of China, over drug cheating claims. Photo: Getty

Sun, who is one of his country’s most famous athletes, was allowed to compete at the world titles in South Korea despite his upcoming hearing in the Court of Arbitration for Sport (CAS) in September that may end the Chinese star’s career.

The 10-time world champion has been accused of smashing vials of his blood with a hammer during a clash last year with testers and faces a lifetime ban if found guilty.

He also served a doping ban in 2014.

The bitter rivalry between the pair, which dates back to Horton’s “drug cheat” comments at the Rio Games, looks set to continue when the pair contest the 800m freestyle heats on Tuesday.

Horton is yet to speak publicly about his podium protest but that may change, with Horton tipped to finally address the medal ceremony controversy after his 800m freestyle heat on Tuesday morning.

Mack Horton took silver against China’s Sun Yang in the 400m freestyle final. Photo: Getty

In the meantime, Horton has had to deal with a savage reaction to his anti-doping stance with Chinese media outlets slamming his protest and social media going into meltdown.

The China Daily led the country’s chorus of disapproval, saying: “Horton’s behaviour was not an insult to Chinese athletes, but an insult to himself.”

Vile messages have also inundated Horton’s Instagram page since Sun claimed the protest was disrespectful to China, with death threats directed at the Olympic champion, his family and even his girlfriend.

However American breaststroke champion Lilly King revealed the Australian received a standing ovation at the athletes’ village for refusing to acknowledge Sun on Sunday night.

“We were kind of waiting around for that awards ceremony to see what was going to happen and yeah it was awesome,” two-time Olympic gold medallist King said.

“When we walked into the dining hall, he walked in after us and like the whole dining hall erupted in applause so it was pretty great to see the athletes united on his stance and supporting him as well.

“I don’t think anyone at FINA’s going to stand up for the athletes so the athletes have to stand up for themselves.”

China’s star swimmer Sun Yang has accused Mack Horton of disrespecting his nation. Photo: Getty

Sun – who claimed a fourth straight 400m world title – reacted to Horton’s stance, saying it was disrespectful to China.

“It was unfortunate because disrespecting me is okay but disrespecting China was very unfortunate and I felt sorry about that,” he said.

-with AAP