The only thing certain anytime Sonia O'Sullivan races Gabriela Szabo is that one of them is going to lose. Almost nothing has separated their confrontations in the past, and nothing suggests it will be any different when it comes to deciding the world indoor 3,000 metre title.

As the eighth edition of these championships gets under way in Lisbon this morning, few events are more eagerly anticipated than the meeting between O'Sullivan and Szabo. There is no greater rivalry in the world of women's athletics, and, as always, both athletes have come here with the sole intention of winning.

There is little doubt that when they meet in the same heat this morning, in what will be their first confrontation since the home-stretch duel in Sydney, it will be of little significance to the outcome in the final. But come late tomorrow afternoon, expect the 8,000 sellout crowd in Lisbon's Atlantic Pavilion to be on their feet.

O'Sullivan is the less familiar face on the indoor circuit, and indeed this will be her first indoor race since allowing Szabo to sneak the gold medal in Paris in the 1997 championships. But when O'Sullivan is running well, she will run well on any surface.

"It makes no real difference to me where I race," said O'Sullivan yesterday, surrounded by her familiar entourage of partner and baby. "I've run good 10km races on the road without racing much on the road and you could say the same about cross country. From the indoor races she's run obviously Szabo is in very good shape. All I know right now is that I'm in as good a shape as I've ever been at this time of the year. And I haven't run against anybody yet who can really bring out the best in me."

Of course, no athlete creates a more competitive fever in O'Sullivan than Szabo. Although six years younger, the Romanian has since 1997 been her greatest rival on the track. The Olympic 5,000 metre dual - so narrowly won by Szabo - was the most recent in a long list of championship bouts. "I definitely run very well when I race against her," added O'Sullivan.

"And I really want to go well against her in a championship race. When you're racing against someone who is as good as yourself then you have to be at your best. I get excited about that and can really focus on the race. Although I don't think too much about the rivalry. I never get on the starting line and think we are the only two in the race.

"But I suppose it is good for the sport. People look forward to watching and it becomes like a boxing match or a tennis match when it comes down to a one-on-one. We are very evenly matched and I can deal with whatever way the race is run. I can run 29 seconds for the last 200 metres as well."

It is somewhat surprising that both athletes have arrived here in similarly competitive shape not long after the Olympics. Szabo has again turned heads with her world indoor record of eight minutes 32:88 seconds in Birmingham last month, while O'Sullivan concluded a most productive winter training in Australia with a solo run of 8.43:51. At this time of the year anyway, most people are running faster indoors.

Although Paris four years ago was O'Sulliavan's only recent flirtation with indoor running, she won the American collegiate 5,000 metre title back in 1992, the year after she also set a world indoor record of 15.17:28 for the distance. Szabo more recently returned to the championships in Japan two years ago, and came home with double gold in the 3,000 and 1,500 metres.

None of those facts have any bearing on O'Sullivan's ambitions: "Once I'm fit and all the training is done then I'm always confident. My biggest thing is that I always believe in myself. The Olympics didn't change that but it has helped in that I was away from those kind of races for over a year. But I was brought right back to that level again at the Olympics."

No one honestly expects it to be anything more than a twoway contest, but there are other elements in the race which deserve some attention. Regina Jacobs took bronze two years ago and comes off the American circuit with the fourth fastest time in the world this year (8.43:88). Russia's Yelena Zadorozhnaya, with a 8.41:44 to her credit, also has the potential to provide the upset.

O'Sullivan has further motivations: "Well I've never won this title. I have gold medals from lots of different things but never the indoors. And when you train hard in the wintertime you need something to look forward to. And of course finishing second in the Olympics got me motivated to come here. I constantly get people saying to me they thought I had her, that they thought I would get past . . . Well so did I."