London: China’s Liu Xiang plans to celebrate his birthday by sending a warning to his Olympic 110m hurdles rivals on his first appearance at the London Grand Prix on Friday.

Liu, a former Olympic champion, is among the leading contenders to win gold at the London Games and he has the perfect opportunity to underline his credentials in the Diamond League meeting at Crystal Palace.

The Chinese star, who leads the world rankings this year with 12.97 seconds, won the Olympic title in Athens in 2004, but left fans devastated when he pulled out of the Beijing Games because of an Achilles injury.

Liu, who turns 29 on Friday, has continued to struggle with injury since Beijing, but he believes he is back to his best after opting for a new stride pattern.

Now, just two weeks before the Games begin, Liu, who also won gold at the 2007 World Championships, hopes to fine-tune his Olympic preparations with victory over outdoor world champion Jason Richardson and world indoor 60m hurdles champion Aries Merritt.

“This will be my last race before the Olympics so I will be looking for a very strong performance. The London Diamond League will be the perfect race for me to complete my preparation,” Liu said.

“I’m really excited to be competing in London for the first time. It’s a great opportunity for me to experience the conditions and atmosphere of the host city just two weeks before the Games.”