BERLIN: American Sanya Richards struck the first blow in her bitter rivalry with Britain's 400m Olympic and world champion Christine Ohuruogu here on Saturday as she beat her in their first round heat at the world championships.

The 24-year-old Jamaican-born naturalised American - who could only take individual bronze behind the Briton in Beijing last year and failed to qualify for the 2007 world championships in the 400m - is determined to end her major title individual drought here and strike a blow against Ohuruogu.

"I want to get the one gold medal which has eluded me (individual 400m world gold), I am trying not to make it pressurised, I am trying to make it fun," she said.

Richards and Ohuruogu coasted down the finishing straight, the former coming off the bend third but looked at ease as she went past her rivals and crossed the line in 51.06 seconds.

However, neither acknowledged each other as they pulled up and left the track as their thinly disguised dislike of each other was clear to see.

Richards, whose season was ruined two years ago when she contracted a rare virus, admitted that her status as world number one and Ohuruogu with her titles being in the same heat was a little bizarre.

"It was a little bit unusual for us to be in the same heat, that rarely happens," she said.

"But I was happy she was there, it gave me a little extra motivation going in which is sometimes needed.

"I made sure I was going to win today, if Christine had been ahead of me and I had the energy I was going to make sure I won and overtook her."

Richards, though, fully expects Ohuruogu, who has struggled with injury and form this season, to be a formidable opponent.

"I expect her to be back to where she was by the end of the meeting, Christine has a great track record of being ready at the major meets no matter what is going on for the rest of the season.

"She is still the Number One competition.

"But Christine is top of my list of rivals."

Jamaica's two-time Olympic relay bronze medallist Novlene-Williams had thrown down the gauntlet in the second heat as the 27-year-old world bronze medalist eased home in 51.55sec ahead of America's Jessica Beard and Germany's Sorina Nwachukwu.

Her compatriot and Olympic silver medalist Shericka Williams fared less well as the 23-year-old came in a fair distance behind Botswana's Amantle Montsho, who was only eighth in the Olympic final.

Russia's 200m 2003 world champion Anastasiya Kapachinskaya - who got the world title on the back of Kelli White's disqualification and herself subsequently served a two-year ban for drugs from 2004 - fought out a duel with Debbie Dunn before giving second best to the American.

Britain's world silver medalist Nicola Sanders was second in her heat behind Russian Antonina Krivoshapka but looked to be in good shape ahead of Monday's semi-finals.