Once again the African runners will provide the main challenge to Sonia O'Sullivan in tomorrow's World Half Marathon championships in Brussels, particularly with the confirmation of leading entries from Kenya and Ethiopia.

It now appears that the race for the women's title will be the most competitive yet seen in the 11 editions of these championships.

Two former winners are among the starters and the only notable absentee is the reigning champion Paula Radcliffe, still on a break after her victory in last month's London marathon.

O'Sullivan, though, is confident that her form has progressed considerably since the World Cross-Country in March and the three-weeks of altitude training in the US was ideal preparation for the 13.1 mile road-race.

Certainly, she is in shape now to take the $30,000 prize, but there are probably a dozen runners capable of upsetting her plans. For a start, there are five strong Kenyan entries, headed by Tegla Loroupe, former three-time winner (1997-99) and former world marathon record-holder.

Loroupe has struggled a little since the disappointing run in the Sydney Olympic marathon, but her experience alone makes her a daunting opponent.

Susan Chepkemei (second to Radcliffe in Bristol last October) and Lenah Cheruiyot (fourth fastest in the world this year) may prove to be the greater Kenyan threat on the day.

Ethiopian hopes lie with Berhane Adere, who took third in Bristol and at aged 28 is enjoying a career second coming (she broke the world indoor 3,000-metre record in February).

Sure to be in the mix as well is South African Elana Meyer, probably past her best, but another former winner and still the second fastest ever.

If the Africans weren't enough for O'Sullivan to worry about, there are also full-strength teams from Japan and Russia. Her Australian training partner Kerryn McCann has also been targeting this race while the locals will look to Marleen Renders, winner of the Paris marathon last month.

Even short of her very best O'Sullivan has the speed to kill off all these runners in the closing stages. The biggest test tomorrow will be staying in contention over the closing miles of a distance still relatively unknown to the Irish athlete.

On the basis of her two previous half marathons (both the Great North Run, where she won in 1998), there is no doubt that O'Sullivan can go the distance.