West Ham released a statement prior to the weekend confirming they held the forward's registration and he is under contract at Upton Park until 2010.
Sir Alex Ferguson insists there will be nothing 'dodgy' in the transfer, following the problems which landed the Hammers with a £5.5million fine for the original deal which brought Tevez, and Javier Mascherano, to England.
There have been suggestions that the Red Devils will sign the 23-year-old on a two-year loan deal, with an option for a permanent deal, rather than spending a lump sum immediately.
Either way, Hammers boss Curbishley is insistent that the East London club must be involved in the decision-making process regarding Tevez's future.
"Obviously, Manchester United are interested.
"Whatever happens has got to go through West Ham, that's the situation.
"I've kept quite out of it, that's for other people and we'll see what happens."