By Ian Gordon, PA Sport, Paris

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Sonia O'Sullivan reckons she will have to run faster than ever before to win a World Championship 5,000 metres medal in Paris on Saturday - but believes she is in the right shape to do just that.

The Irish runner notched a season's best of 14 minutes and 55.50 seconds in the Stade de France on Tuesday night as she qualified for the final by finishing second in her heat - one place ahead of 10,000m gold medalist Berhane Adere of Ethiopia.

It was an impressive run from the athlete who missed the first four months of the season with an Achilles injury and then struggled to recapture her best form.

O'Sullivan led for the first half of the race before settling back into the pack, and she made her charge for the line 200 metres from home.

"That was a good race because it had a bit of everything," said 33-year-old O'Sullivan. "I was a bit nervous before the race, but now I feel really good.

"I am glad to have got it out of the way and now I have to go away and think about the final because I imagine it will be a faster race than I have ever run before.

"I am going to have to go out there and run as hard as I can. I need to be in there for when it becomes a race because that is my strength, when it becomes a race.

"It is never easy to run faster than you ever have before, but I've been trying to do that for a few years now and it will be a big challenge, but I'll be going after it and I'll be there Saturday."