Keane, the former Sunderland and Ipswich manager, has been linked with a post as Paul Lambert's number two at Villa Park over the past week.
The 42-year-old had previously been a contender for the manager's position at Celtic but withdrew from consideration.
O'Neill believes Keane could combine his role with the national team with new duties at Villa but does not want the matter dragging into next season.
O'Neill, quoted in the Irish Independent, said: "I want to be careful about jumping the gun because we had him signed, sealed and delivered to Celtic and that did not materialise.
"I don't really know if this is something that he is going to have a serious look at.
"But if he is then I will definitely speak (again) to Paul Lambert - and see if that kind of role can be combined.
"One thing I want to establish is what sort of in-depth conversations have gone on.
"I have spoken to Paul Lambert. Paul has spoken to Roy about the possibility of it happening.
"Nothing definitive has happened and I don't really know what sort of commitment (the Villa position) would entail.
"If he is actually a full-blooded assistant then that is something to consider.
"I don't mind it (speculation) going on for a week or two. Celtic wanted something in place as they have games coming up quite soon.
"And I assume Aston Villa will want to get something in place by the time they start pre-season.
"I don't want it to be continued right through until August time."
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