A doping scandal sparked by 23 Chinese swimmers who tested positive for a performance-enhancing drug has cast a shadow over the Paris Olympics and sparked a huge row between the global and American anti-doping agencies.
Here's what you need to know about it:
WHAT HAPPENED?
The swimmers were cleared by a Chinese investigation which said they were inadvertently exposed to the drug through contamination. The investigation determined the swimmers were staying at a hotel where traces of TMZ were discovered in the kitchen.
The World Anti-Doping Agency said it had no evidence to challenge China's findings and that external counsel had advised against appealing them. The incident was not made public at the time.
Some of those swimmers went on to win medals in Tokyo and are competing at the Paris Olympics.
The United States Anti-Doping Agency has accused the World Anti-Doping Agency of covering up the scandal and called for the body to be reformed.
China's Foreign Ministry spokesperson Lin Jian said this month that this was a "non-existent case that the U.S. keeps selling" with the aim of "degrading" Chinese athletes and "obstructing their participation in the Paris Olympics".
Beijing has expressed its full confidence in WADA.
DID WADA MISHANDLE THE CHINA CASE?
Two independent investigations, one by Swiss prosecutor Eric Cottier looking into WADA's handling of the case and the other an audit by World Aquatics reached similar conclusions that there was no mismanagement or cover-up.
But the United States Anti-Doping Agency remains unconvinced about the findings and has accused the global agency of mishandling the case and urged the U.S. Department of Justice (DOJ) to investigate.
WHAT IS THE U.S. DOING?
Any DOJ investigation would fall under the Rodchenkov Act legislation passed in 2020 that extends U.S. law enforcement jurisdiction to any international sporting competitions that involve American athletes or have financial connections to the United States.
Named after Grigory Rodchenkov, a former Russian anti-doping laboratory head who turned whistleblower, the act criminalises doping schemes intended to influence sports events and allows U.S. prosecutors to seek prison terms of up to 10 years and fines of up to $1 million.
WHAT DOES WADA SAY?
WADA has defended its handling of the China case, saying it had been guided by science and expert consultations.
It says the Rodchenkov Act undermines global anti-doping rules and that unilateral U.S. investigations, "encouraged by USADA" risk isolating the U.S. from global sport.
On Wednesday WADA told Reuters it was taking the U.S. agency to the Independent Compliance Review Committee next month in a move that could jeopardise the country hosting the 2028 and 2034 Olympics.
Any country wanting to compete in or stage an international sporting event must be compliant with the world anti-doping code, meaning if the review went against the U.S. it would have to forfeit participating in and hosting the Games.
HOW IS THIS AFFECTING THE OLYMPICS?
The International Olympic Committee, which founded WADA and covers half the agency's operating costs, has tried to calm the storm and told the United States to fall in line or forfeit its right to host the Olympics.
The IOC said on Wednesday that an amendment in the host city contract for the 2034 Games in Salt Lake City had been added that would allow it to terminate the deal "in cases where the supreme authority of WADA" is not respected.
America's top Olympic Official, Gene Sykes, on Thursday declared the United States' unwavering support for WADA and asked for a cooling of tempers.
