LaShawn Merritt, who has served a doping ban, on Thursday failed to take the trash-talking bait laid by Britain's Dai Greene, a likely rival in the 4x400m relay at this summer's London Olympics. The 25-year-old American was banned for 21 months in October 2010 after testing positive for the anabolic steroid DHEA in three tests between October 2009 and January 2010. His lawyer claimed the drug had been contained in an over-the-counter penis enlargement product and that Merritt had therefore consumed it inadvertently. The one-lap specialist was then cleared to compete in the London Games after the Court of Arbitration for Sport (CAS) said that the rule banning athletes suspended for doping for six months or more from competing at the Olympics was "invalid and unenforceable". Merritt's ban was back-dated to October 2009 and he returned to competition in July last year, promptly going on to claim silver in the 400m at the world championships in Daegu, South Korea, a month later. But that has not stopped Greene from lining Merritt up squarely in his crosshairs, the reigning 400m hurdles world champion calling the American a "liar, thief and cheat". "If I'm in the relay team and we reach the final then there's every chance we'll be lining up against Merritt," Greene said in March. "I'll tell you now, I'll happily go and find him at the start and tell him to his face, "You're a cheat and you shouldn't be here". Greene warned: "I'll be so motivated, so pumped up by his very presence in the race that I'd do anything I could to find myself up against him in the same leg of the relay, no matter what leg it would be. "It won't be a surprise if we're against each other in the semis or the final. So it's likely I'll get my chance to do this. And if I do, I'll take it." But Merritt, speaking ahead of Friday's opening Diamond League meeting here, said: "If he comes up and says that, I'll wish him well, get my 400 group together and go at it. "That's the only thing to do. After the talking it's time to line up and run the race and that's what I'll be doing." Greene accused Merritt of having committed a "massive offence", saying drug cheats were taking the places of honest athletes, something that he argued affected sponsorship, income, and the "ability to become the best". "They are no more than thieves, stealing from athletes who work so hard for the love of their sport," Green said, also accusing Merritt's penis enlargement product excuse as "nonsense". But Merritt refused to be drawn on the Welshman's accusations. "It's another person's opinion," he said. "I don't have anything to do with him and he's got nothing to do with me. "He's not going to stop my training or break my confidence in any way. I'm still going to do what I've got to do." Angelo Taylor, the two-time Olympic 400m hurdles champion who will race the 400m here as the season slowly gets under way, added that the "trash-talk" over the 4x400m relay had not affected the US team. "There's been a lot of trash-talking on the circuit about the 4x400m relay, about how the US is going down this year, but ... I'm very confident in the guys we have," he said. "We own the 4x400m," said Taylor, a relay gold medallist in Beijing and a three-time world relay champion. "Everybody gets up for a race in different ways, talking the trash talk, and I'm the type of guy that just lets my performance do the talking for me. I'm going to be ready." Merritt added: "Olympic year is the pinnacle, it's the year that makes track and field athletes. You train hard but never write anybody out."