Hopefully we can convert this into a series win because that's the important thing Kevin Pietersen

Kevin Pietersen said Alastair Cook could end his career with 40 Test centuries after hitting his sixth, at the tender age of 22, on Saturday.

Cook's 106 forced West Indies to chase 455 to win over the last three days.

And Pietersen, who hit 68 in a stand of 122 with Cook, said: "Who knows where Cooky can go at such a young age?

"He's playing so well and the sky's the limit for him. We all go through rough times but there's no reason why he can't get 30 to 40 hundreds."

Nobody has ever hit 40 Test centuries. Sachin Tendulkar, still playing at the age of 34, leads the way with 37.

Cook himself typically underplayed his achievements.

He said: "I'll just try and keep working hard and keep scoring runs. My next big challenge is to get a really big hundred.

"The wicket's doing a little bit but we were in a really good position overnight.

"Most Test cricket [does not require] too much urgency - it's just for me to bat and bat.

Aware that he had become the first Englishman to score six hundreds in Tests before reaching the age of 23, he added: "Anyone who says they're not a stats man is a liar.

"But [stats] don't really drive me. I got a bit of luck along the way but hopefully we can convert this into a series win because that's the important thing.

"We are in a really good position but anything can happen and we have to expect a really tough battle."

England need nine more wickets after the inconsistent Steve Harmison removed Daren Ganga to leave the tourists 22-1.

"Steve bowled very nicely," said Cook. "He's having a tough time at the moment so it's important we as a team get behind him.