BERLIN, August 18, 2009 (AFP) - Jamaican sprint king Usain Bolt will bid to continue his attempt to emulate his Olympic feats on the world stage on day five of the World Athletics Championships here on Wednesday.

Fresh from setting a new world record of 9.58sec for the 100m on Sunday, Bolt races in the semi-finals of the 200m, with the final slated for Thursday, and looks the firm favourite to claim the sprint double here.

In the absence through injury of American rival Tyson Gay, the US team is relying on Athens Games gold medallist Shawn Crawford and reigning world bronze medallist Wallace Spearmon to harry Bolt in the sprint-off between the two countries.

There are also four finals in the evening session - the men's discus and 1500m, and the women's 100m hurdles and 800m.

American Dawn Harper will have a chance to add world gold to her Olympic title in the women's 100m hurdles if she first manages to negotiate the semi-final.

All the 25-year-old's main rivals, including Australia's Olympic silver medallist Sally McLellan, also progressed to Wednesday's semis with the final scheduled for 1915 GMT.

The women's 800m will be run without Olympic champion Pamela Jelimo, who pulled up in her semifinal for the event.

That hands the teenager's compatriot, defending world champion and Olympic silver medallist Janeth Jepkosgei, an outside chance at a podium spot although her form has not been great.

All eyes, however, will be on 18-year-old starlet Caster Semenya, who has burst onto the South African scene this year taking both the junior 800m and 1500m titles with vastly improved times and has proved to be the runner to beat here.

The men's 1500m could all come down to team tactics.

Defending champion Bernard Lagat, along with American team-mates Lopez Lomong and Leonel Manzano, form a dangerous trio.

But they will be up against Moroccans Amine Laalou, Mohamed Moustaoui and Abdelati Iguider, as well as the Kenyan duo of Olympic silver medallist Asbel Kiprop and Augustine Kiprono Choge.

Estonian Gerd Kanter, the reigning Olympic and world champion and also the only thrower to exceed 70 metres this season, is the only real favourite for the men's discus title.

Kanter is on a 28-meet win streak and is naturally unbeaten during 2009, and his closest rival will likely by Lithuanian veteran and former double Olympic champion Virgiljus Alekna.

The men's decathlon also kicks off with the first five events of the gruelling 10-discipline event.

The decathletes will compete in the 100m, long jump and shot put in the morning session, with the high jump and 400m coming in the evening session.

Everything points to a new major championships winner, with reigning Olympic champion and 2005 Helsinki worlds winner Bryan Clay out with injury.

It would be a big ask of reigning world champion Roman Sebrle of the Czech Republic, sixth in Beijing, to repeat his achievements from Osaka in 2007.

The biggest favourite will be 21-year-old Cuban Leonel Suarez, the Olympic bronze medallist who won the Caribbean Championships with a national record 8654 points, also the world-leading mark.

There are also qualifying heats in the women's discus and 5000m, and in the high jump and 110m hurdles for the men.

The busy evening schedule sees male athletes also competing in the semi-finals of the 400m, and women in 200m heats.