Former Aston Villa defender Carlos Cueller is the only new face at the Stadium of Light so far this summer, whilst Asamoah Gyan completed his permanent move to UAE side Al-Ain earlier in the week.
The squad fly out to Korea next week to take part in the Peace Cup tournament, so O’Neill is not expecting any developments until the team return to England but says he is keen to “add a couple of fresh faces” ahead of the new season.
He told The Journal: "When we come back from South Korea, I would expect the situation to change.
"We are obviously in the market to try to strengthen our team, of course. I think that's pretty obvious - all football clubs will be trying to do that.
"But for us, it would be nice to add a couple of fresh faces - not just for the sake of it, but to improve the quality of the squad, which is what we are trying to do."
Real Mallorca defender Ivan Ramis has been linked with a move to Sunderland and Aston Villa recently with Wolves striker Steven Fletcher also reportedly interesting O’Neill.