West Ham managing director Paul Aldridge told the club's official site: "We have had an offer accepted by Nottingham Forest but we have not spoken formally with Marlon or his agent yet and it is far too early to say whether a deal will be completed,"
Harewood has put in some dire performances recently but did manage to put the Reds in front against Wigan at the weekend.
He has also allegedly had bust-ups with three first-team players in the last six months but is still a fans favourite at The City Ground.
The deal is believed to also include a sell-on clause similar to the transfers of Jermaine Jenas and David Prutton to Newcastle and Southampton respectively.