RIO DE JANEIRO (AP) It's a bitter grudge that has lasted for years: Aaron Cook vs. Britain.
Born and raised in the U.K., Cook is now a citizen of Moldova and will be fighting for that country in the men's 80-kilogram competition in what his British opponent Lutalo Muhammad describes as ''probably the biggest rivalry in taekwondo.''
Cook trained at Britain's national academy but abandoned it ahead of the London Games after a coaching dispute. When it came to picking the Olympic team, British officials snubbed the top-ranked Cook in favor of 56th-ranked Lutalo Muhammad, who went on to win a bronze.
Cook said he was heartbroken and felt cheated out of an opportunity to fight at his home Olympics. Some critics, however, said his diva-like tendencies were unbecoming of the Korean martial art, which values modesty and respect.
Last year, Cook switched nationalities after the president of Moldova's taekwondo federation offered to pay for his training and expedite his passport so he could represent the former Soviet republic at international competitions.
Muhammad says he would relish the opportunity to fight Cook, especially after he and his family received hate mail and abuse from Cook supporters after his Olympic selection.
''We are not friends,'' Muhammad said. ''There's always fireworks when we fight.''
Both 25, they have fought four times and split victories evenly.
''That makes it even more tasty for a fifth fight,'' he said.
Cook won a bronze for Moldova at last year's world championships, losing to Muhammad's teammate, Damon Samsun, who took silver. Muhammad was sidelined with a knee injury but defeated Cook at a competition in Mexico, where he also secured an Olympic spot for Britain.
Anything between the two athletes should be settled on the mat in Rio, Muhammad said. Still, he called his rival a ''world-class fighter.''
''He's always going to be dangerous,'' Muhammad said. ''Do I think I'm better than him? Absolutely. The place to prove that is in the ring.''
Cook's explosive strategy, which combines spinning kicks with a relentless attacking style, has been difficult for many competitors to counter, but Muhammad has been more successful than most. Using his height advantage - he is about two inches taller - has helped Muhammad neutralize Cook's theatrics, especially when he unleashes lightning-fast head kicks of his own off his forward leg, giving his opponents little time or distance to react.
The Cook-Muhammad rivalry will bring more fans to the sport, said Jean Lopez, head coach of the U.S. taekwondo team.
''It's always good for sport when there's a perceived rivalry between a hero and an anti-hero,'' he said, without specifying which roles Cook and Muhammad were fulfilling.
Other fighters recognize the intense rivalry between the two but warn that it might be counterproductive for them to focus on it at Rio.
''If you let it get to that stage where it becomes a big rivalry, you'll start doing things uncharacteristically,'' said Safwan Khalil, an Australian taekwondo athlete who knows both Cook and Muhammad well.
Competitors sometimes become reckless if their fights are driven more by emotion than by strategy, he added.
Khalil's advice for Cook and Muhammad is to focus on their first fights Friday, rather than each other, saying that both have formidable opponents in the preliminary rounds.
''If they happen to win all three matches, they'll meet (in the final),'' Khalil said. ''I think they'll worry about that later.''
Indeed, Cook mostly has refrained from talking about Muhammad recently and appears focused on his second Olympic appearance; he narrowly lost out on a bronze at the Beijing Games in 2008.
But for Cook, nothing less than a gold medal in Rio will do.
''It would just be a lifetime achievement,'' he said in a recent TV interview. ''We've been in it as a family since the start. It would just be really special.''