Gibson was sixth in the 100m breaststroke at the Athens Olympics

Gibson has struggled to recapture the form that won him 50m breaststroke gold in Barcelona two years ago.

"It's going to be very difficult for me to go and defend my title. But I'm a fighter and any event I swim in I know I've got a chance of winning," he said.

"It's a different sort of pressure this time round. I get the feeling everyone is looking at me to deliver this time."

Gibson's victory in Barcelona made him the first Briton to win gold at the world championships since David Wilkie in 1975.

But he is set to face fierce competition this time, with in-form German Mark Warnecke favourite for the final on 27 July.

"The 50m is such a hit-and-miss event and if you get it right you can become world champion like I did," said Gibson, who was sixth in the 100m breaststroke at the Athens Olympics.

I've had a good year's training since Athens and I'm really looking forward to this meet Britain's David Davies

"I took my time getting back in the pool after Athens. Psychologically I still don't think I'm right from what happened and I've not really committed to this year as well as I could have done.

"If that affects my results this year but puts me in better stead in 2008 for Beijing then it's a sacrifice worth making."

Britain claimed eight medals - including two golds - in Barcelona two years ago.

And national performance director Bill Sweetenham is predicting more success in Montreal despite an Olympic haul of just two bronzes.

Davies earns 1500m bronze

David Davies, one of those two Athens medal winners, is expected to go well in the 1500m freestyle.

But to claim gold he will have to see off the world record holder Grant Hackett, who stormed to victory in Athens and has been unbeaten in the event for eight years.

"I've had a good year's training since the Olympics. I want to achieve more things, and I'm really looking forward to this meet," 20-year-old Davies told BBC Five Live.

"I've adapted a bit so hopefully I can get out a bit faster and get closer to Hackett without blowing a fuse.

"The fact that he's around for the next four years is really tough work for me and he's not going to give up his throne easily."