The Hammers outlined their desire to sign Sidwell last week and a fee was soon agreed, but now the deal looks in jeopardy.
Boss Avram Grant said: "I like Steve. I worked with him at Chelsea, he never let me down and he's a good person.
"But January stories, part of them are true and part are not. I have nothing to say until the deals are done.
"We have followed many players like many clubs, we are following players to make us strong, but we will not bring in 15 players, not even five."
Source: PA
Source: PA