United have been linked with strikers Nicolas Anelka and Dimitar Berbatov but Ferguson told Inside United magazine: "I think the squad is good enough."
He added: "We do not always get great joy in January. It takes time for players to settle in.
"Look at what happened with Patrice Evra and Nemanja Vidic."
However, Ferguson did concede he may require cover in defence, as his side pursues trophies on three fronts.
"Maybe we are short of cover in the left-back area now Gabriel Heinze has left, but other than that, we are OK," he added.