MOSCOW - Olympic champion Felix Sanchez's bid to become the first man to win the 400 metres hurdles world title three times got off to the ideal start at the World Athletics Championships on Monday as he eased into the semi-finals.

While the 35-year-old from the Dominican Republic -- who also won the Olympic title in 2004 -- was on cruise control, Britain's defending world champion Dai Greene struggled to even make Tuesday's semi-finals. The 27-year-old Welshman, who missed out on a medal by one spot in the Olympic final, said he had been suffering from a fever. Sanchez, whose tears at the Olympic medal ceremony were one of the iconic moments of the Games as he sobbed at the memory of his late grandmother Lilian who brought him up, said it was too open a race to start making predictions.

"It's bound to be a close race as we have all been close to one another this season," said Sanchez, whose resistance to retiring during several years in the doldrums paid off handsomely. "If I win here I will be the only man to have won this title three times (he won in 2001 and 2003) and if I win a medal I will have four (he won silver in 2007) and be the most decorated athlete in the event's history."

Greene struggled through his heat and was edged out of the automatic qualifier spots but got lucky as Puerto Rican Eric Alejandro was disqualified, allowing him to progress to the semi-finals. "I've had a tough last two weeks. I haven't had a chance to do as much as I'd like," said Greene. "It's been a nightmare the last couple of days, to be honest, and we were wondering whether I'd be good enough to run today, we didn't really know what I'm capable of.

"Now we've got the answer and it's not an answer we like. "Fingers crossed I can rest up and put in a better performance tomorrow. "I came down with a fever on Friday night, I was bed-ridden pretty much for all of Saturday, I'm now trying to eat and drink as much as I can." Sanchez and especially Greene will have taken note of some impressive performances among their rivals, including another former two-time champion Kerron Clement, his US team-mate Michael Tinsley, the silver medalist in London, and Puerto Rico's Olympic bronze medalist Javier Culson.

A live contender from outside the established ranks could well be Senegalese Mamadou Hanne, who won his heat in style leaving 2005 world champion Bershawn Jackson trailing in his wake. Hanne, 25, said his career had taken off since he moved to France to study two years ago and he had also called on a Senegalese athletics great for advice.

"I took up athletics pretty late and these are my first world championships," said Hanne, who reached last year's Olympic semi-finals. "However, thanks to the advice of my compatriot Amy Mbacke Thiam, who won the women's 400m gold in 2001, and who is here with me, I am getting used to the atmosphere and how to prepare for it."

All three Olympic medalists from the women's 400m hurdles made it through to the semi-finals. Champion Natalya Antyukh, finished third in her heat, while silver medalist Lashinda Demus and Czech bronze medal winner Zuzana Hejnova, the fastest woman this season, also looked in good shape. Likewise both of the favourites for the men's steeplechase had no problem in reaching Thursday's final.

Two-time Olympic gold medalist and two-time world champion Ezekiel Kemboi coasted through his heat to finish second while his close friend and Olympic silver medalist Mahiedine Mekhissi of France posted the fastest time of 8min 15.43sec.