The element of surprise is never far away from Sonia O'Sullivan when it comes to championship running. And it surfaced yet again yesterday when she announced her intentions for a World Indoor Championship double over 1,500 and 3,000 metres in Lisbon.

It was expected that the challenge of facing Gabriela Szabo in this afternoon's 3,000 metres final would satisfy O'Sullivan's interest in these championships. Now she feels that she has the fitness and speed to also declare for the 1,500 metres, the heats of which start an hour and 45 minutes before the 3,000 metres final.

If everything goes to plan, she will be back on the track tomorrow afternoon in the 1,500 metres final, hoping to achieve a double that would earn her $80,000.

Her plan, which surprised almost everyone in Lisbon's Atlantic Pavilion, is ambitious even by O'Sullivan's standards. Given the manner in which she breezed to victory in her 3,000 metres heat yesterday morning, however, it's certainly not impossible. The win has already provided her with a slight psychological edge over Szabo, who finished a close second but seemed to concede to O'Sullivan's acceleration on the last lap.

"Well, I am going to take one race at time," O'Sullivan later explained, "but I definitely think it is possible to do the double. I had to make a decision on what races I would enter on Thursday and I knew I would be committed to both races. But I am happy with the decision, and as far as I'm concerned, the 1,500 metre heats will just be a warm-up for the 3,000 metres final."

But it's hard to know just how much the effort in the 1,500 metres heat will detract from O'Sullivan's chance of gold in the longer distance. She ran perfectly in yesterday's heat, sharing the pace-setting chores early in the race and then sitting relaxed near the back of the field once the positions settled. Approaching the bell in seventh place, she then slid outside and shifted into the lead, scattering the leading pack in her wake.

Covering the last 200 metre lap in 29.7 seconds, O'Sullivan finished in eight minutes 55.79 seconds. Szabo had stayed near the front throughout the race and took second in 8:55.84. Finishing just behind them were Olga Yegorova of Russia and Regina Jacobs of the US, both of whom are likely to have another say in this afternoon's final. It was a bizarre computer calculation that put so many of the leading contenders in the same heat.

"I have to be happy with that. I knew it was top five to qualify and that's all I wanted to do, and make it safe by not falling down or anything like that. It's early in the morning and the longer it went the better I felt. That was also my first indoor race in four years. There's no way I was all out at the finish and I actually eased down at the line."

Szabo was actually successful in a similar double in the last championships in Maebashi, Japan two years ago but on that occasion there were no heats in the 3,000 metres. Despite some expectations that she would attempt a similar feat here, the Romanian has made the 3,000 metres her sole target. She has won the event in the previous three championships.

There were also suggestions over the last couple of days that the 1,500 metres may not require heats, but it will now involve two races of nine runners, with the top three in each and then the three fastest losers progressing to tomorrow's final. Although she had been keeping the decision to herself, O'Sullivan in fact decided to target both events with her coach Alan Storey after her final training session in London last Tuesday.

"I certainly won't be thinking about the 3,000 when I'm in the heat of the 1,500. I haven't seen the field and I don't want to see it either. And there's plenty of time to recover. I've done hard sessions on the track when I've only had a minute and 45 seconds to recover."

Qualification won't be easy, as she has drawn, among others, former world champion and home favourite Carla Sacramento, along with the feared Romanian Violeta Beclea-Szekely. And there's no notion of O'Sullivan opting out of the 1,500 metres at this stage. Under new IAAF rules, athletes must compete in every event in which they are declared or they face disqualification from subsequent events on the programme. They must also be judged to have given a legitimate effort in each race or they may face similar disqualification.

Of course, an attempt on such a double is hardly unusual for O'Sullivan. She brought home two gold medals from both the World Cross Country Championships and the European Championships in 1998, and last September attempted to win another medal over 10,000 metres after taking Olympic silver in the 5,000 metres. But never before has she juggled with such a narrow and demanding timetable.