ESTORIL, Portugal (AFP) - MotoGP star Valentino Rossi is confident of kick-starting his season with a successful defence of his Portuguese Grand Prix title at the Estoril circuit on Sunday.

The Yamaha rider is sitting third in the standings, ten points behind Spaniard Dani Pedrosa who took the world championship lead after winning at Jerez two weeks ago in front of the Italian.

But despite being boosted by his success at home Honda's Pedrosa has to contend with a rampant Rossi who has won here five times and finished on the podium in each of his last eight visits.

The pair had a terrific duel last year with the Spaniard crossing the line just 0.175sec behind Rossi.

Rossi said: "Since 2000 I've always been on the podium here. I like this circuit. This weekend will be difficult but after the good result from Jerez I'll try and continue on the same track."

But the Italian is aware that other riders could also challenge, including his Spanish teammate Jorge Lorenzo.

"This year a lot of riders can win, the championship is more balanced and I expect the second group to battle to try and be up there with us," added Rossi.

Lorenzo is second overall, five points behind Pedrosa, and despite being new to motorcycling's top category, has reached the podium twice - runner-up in Qatar and third in Jerez.

But the new Spanish star of motorcycling remains modest.

"I've never done better than third in Estoril and I still haven't tested this circuit with MotoGP," said Lorenzo. "It's a new challenge. My aim remains the same - to learn, have fun, improve and to do my best."

Pedrosa addded: "Things went very well in Jerez. We'll see how they go this weekend. The (weather) forecast isn't very good but I'll try and do my best," said the Spaniard.

"Last year it was a tough battle with Valentino on this curcuit which is unique - very fast in certain parts and very slow in others."

World champion Casey Stoner is fourth in the championship, one point behind Rossi, after finishing just 11th in Jerez, his worst placement since racing for Ducati.

The Australian will desperately be trying to make up lost ground in the third race of the season.

"It's a track with parts that are fluid and others which are very slow," said Stoner. "It's difficult but really good for the rider. In theory if I work well I can be part of the battle for victory."