The Hammers forward faces some stiff competition for one of the attacking places on the plane to South Africa.

Although Cole, 25, came on to win his fourth cap during the friendly against Slovakia, he did not make the squad for the Croatia game, which Fabio Capello's men won 5-1 to book a spot in the finals next summer.

Having been prolific for the under-21s, Cole is hoping to continue his progression in the full national squad.

That, though, will only come on the back of a consistent campaign for the Hammers, for whom he netted 12 goals last season.

"Carlton Cole has worked very hard on his game and on his mentality and has produced some results," said Zola, who was a team-mate of the 6ft 4in striker when they were at Chelsea.

"Now, all I can say about Carlton is that it all depends on him, because he has all the qualities.

"He is strong, he is quick, he is technically very good, so if he keeps focused on what he is doing, then of course he can be there.

"Capello knows him and certainly is keeping an eye on him."

Zola added: "I can see improvements and I am sure that he knows that, if he wants to play for England, he will have to work even harder, because the people who are playing in his position are also doing well.

"Obviously you can't ask him for everything straight away, but he is working on his game and knows there are areas that he needs to improve.

"He knows that finishing is one of the things he has to improve, but in the last year he has been much better.

"He needs to work on his consistency and to keep scoring continuously, and that will be good for his confidence, for his game and for me.

"We just need to give him the time and tranquillity necessary to produce the results."

Zola, who takes his side to Wigan tomorrow, has now been in the Upon Park hot seat for a year, during which the club has come through some difficult times off the field, their Icelandic owners feeling the impact of the tough financial climate.

"It's been very good and is an achievement, but I want to share it with the club," said Zola, happy to have avoided the predicted fire sale of all his key men.

"[Technical director] Gianluca Nani and [chief executive] Scott Duxbury have been brilliant.

"They believed in the project and never gave up on the idea of keeping the best players and actually trying to improve the team.

"That has been really good and I appreciate that.

"Also, in those moments when it was easy for them to say 'Oh well, maybe we made the wrong choice and need to pick up a new manager'."

Zola added: "Obviously when things are not going very well, you have doubts, but at the end of the day, the enthusiasms were bigger than the doubts so I kept going.

"I really put my head down and kept working hard.

"I kept believing in the way I want to play and we came out very well from that situation."