West Ham co-owner David Sullivan is targeting at least one new forward after the club announced that Andy Carroll will be sidelined for four months.

The 25-year-old confirmed on Thursday evening that he would require surgery on the problem and will now sit out the start of the season for the second year in succession.

Having missed a large part of the previous campaign with an unrelated foot injury, the club-record signing has played just 16 times for the Hammers since joining on a permanent deal from Liverpool last summer.

After initially being ruled out of the two friendlies during West Ham’s current tour of New Zealand, the east London club have now confirmed he will be missing for much longer.

“West Ham United can confirm that Andy Carroll will have an operation on ligaments in his left ankle in the United States on Friday,” a statement on the club’s official website read.

“The England international will then have a week of recovery before starting an intensive period of rehabilitation, which is expected to take four months. “The club would like to again make clear that this is a new injury and not in any way associated with the injury he successfully overcame at the end of last season.”

Manager Sam Allardyce has already moved to increase his options in attack even before Carroll's latest setback — with Mauro Zarate on board and only a work permit application standing in the way of Enner Valenicia's move from Pachuca.

But now Sullivan is determined to see another forward join before West Ham’s season gets under way at home to Tottenham.

“We have to bring in another striker and we’re working on it now to buy one, or loan one, or both,” he said.

“You can never have enough strikers and really with Andy gone we haven’t got enough. It was desperate last year... We probably made a mistake by putting all our eggs in one basket.

“We can’t start the season with the strike-force we’ve got. I don’t think it’s good enough, there’s not enough height in it and if we get another injury, in terms of quantity, it’s insufficient, so we have to sign at least one more player.”

Carroll, who had tweeted on Thursday evening that he was ‘absolutely devastated’ to be injured again, has now said he will strive to return as soon as possible.

“I’m gutted to be missing the start of the season after working hard during the summer and pre-season,” he said.

“Although this obviously isn’t the news I would have wanted, I’m determined to come back fitter and stronger than ever before. I will be doing all I can to get back on the pitch with the lads as soon as possible.”

The latest problem again shines a light on the former Newcastle striker’s initial move to West Ham, with Sullivan admitting it was a risk to spend so much on one man.

The record fee for Carroll meant there was little left in the coffers for Allardyce, who ended up re-signing Carlton Cole after initially deciding not to offer the England international a new deal, due to his lack of options.

“Had we known what we know now we wouldn’t have signed the player,” Sullivan said.

“But it’s easy to be wise after the event. We were assured by our physio — who has since left the club — that the player would be available for the start of the season.

“He wasn’t available until January or February. A mistake was made and we were given the wrong information. We based our decision and our purchase of the player on what the medical department told us.

“We’ve changed everything in that department as a result of that. At the same time on his day he is a devastating and fantastic player, we’ve just got to get him back to his best.”

Although Monaco’s Lacina Traore, who came close to a loan move to the Hammers in January, is reported to be a target once again his own injury issues are likely to leave West Ham wary of having another expensive acquisition on the treatment table.

There are also concerns over one of Allardyce’s summer recruits after the 59-year-old confirmed Senegal midfielder Cheikhou Kouyate requires a scan on his own ankle injury suffered in the 2-1 friendly defeat to Wellington Phoenix.

“Cheikh and James (Tomkins) have stayed behind in Auckland because they’ve got injuries that mean we’ve left a physio with them,” said Allardyce.

“Cheikh has gone for a scan to make sure there is no more damage than we’ve initially assessed medically — Cheikh was caught just above the ankle when the boy tackled him and he was rather fortunate he didn’t break his leg, so we’re pleased about that.”