Ricciardo issues warning to Hamilton

With their Renault powered package predicted to be a threat, the Aussie driver has been training hard in January, putting emphasis on trying to be at peak physical performance in line with the new regulations that will increase the speed of the car.

"I think we can challenge, yes," he told Formula1.com.

"If we make the same improvements we did last year then he (Hamilton) won't have anything easy, believe me.

"It's been fun to put even more emphasis on January training this year - especially when you do it in Los Angeles!

"This year we can afford to train harder and not worry so much about weight and muscle."

Ricciardo, who finished third on the Drivers' Championship last year, said that he is still having fun besides the intense demands of his training regime.

"It's fun. You still can't let it get out of hand, but the intensity has risen and I can also eat a little more after I've trained, which makes me feel good!" he exclaimed.

"What do I do? Everything! From cycling, strength training in the gym, boxing... The list goes on and on."