O'Neill has revealed another club approached him about signing Westwood on loan.
"I haven't heard of an interest from Hull," O'Neill told the Sunderland Echo. "But Keiren clearly wants to play some games, of course he wants to play.
"My situation is that I have a very good goalkeeper in reserve, but it is hard to drop Simon Mignolet when he is playing so well.
"The fact is I'm very reluctant to let anyone go because we simply don't have the back-up.
"A manager did ask me about Keiren a few days ago - rang me manager-to-manager, which seems to be very rare these days - and I just had to to tell him we couldn't do anything."