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.”

Meanwhile, the board are looking to offer Ravel Morrison a new contract despite Allardyce saying the young midfielder is not part of his plans.

“Sam has said Ravel is not part of his plans but we do — as a board — see him as part of our plans,” said Sullivan.