The Senegal international defender is expected to join the Wearside club on loan until the end of the season, but O'Neill has refused to comment on his future after the loan spell is over.
He told reporters: "He's a lad who went out to the Middle East from Rennes and we've made a number of inquiries about his position.
“At this stage, that's as far as it's gone. We've talked about the possibility of a loan until the end of the season. Beyond that, it would depend on performances and things like that.”
The 29-year-old will be joining from Al-Hilal in the Saudi League, and his signing will, it is believed, pave the way for the departure of Titus Bramble.
Meanwhile, O'Neill has praised new signing Alfred N'Diaye from Bursaspor.
“He's athletic, he can cover a lot of ground and while I think there's room for improvement in technique, that's something he wants to do,” O’Neill added. “I feel he can give us that sort of athleticism and vitality around the pitch that sometimes we feel as if we're missing.
"If he shows the same determination as I believe he has, I think there's only one way for him to go and he wants to do it.
“Naturally, you'd like him to settle in and be brilliant immediately, but he'll do really well for us. He'll be a great signing, he really will be.”
Sunderland have also been linked with a move for Swansea striker Danny Graham, who is thought to be on his way out of the Liberty Stadium.