Harewood will certainly not sign in time for Saturday's trip to Nottingham Forest but McCarthy believes an addition of his quality could make all the difference.
The Wolves boss told the club's website: "I've had a discussion with Martin O'Neill and I'm waiting to have another discussion with him.
"I've asked him the question and we'll be speaking again over the next couple of days.
"I'm delighted with the four strikers I've got here - they're all off on international duty and potentially involved in two games - but if I've got the ability to sign somebody of Marlon Harewood's ability and strengths then it would be fantastic."
Villa manager Martin O'Neill added: "Wolves have asked about Marlon on loan and they are one of a number of teams. I have spoken to Marlon about it and it is a possibility.
"We now just have the league to worry about and I can recall him after 28 days. I think it might be beneficial for the likes of Marlon to go out on loan.
"I hope the international break coming up doesn't afford a load of injuries but, in the long term, if Marlon goes and plays four or five matches and is then recalled here, he will be in good physical condition.
"I think the benefits outweigh the possible downside of it.
"He came and asked me about it. Mick McCarthy phoned me about it and Marlon had the choice and we will see. It hasn't gone through yet and I am waiting until after Sunday's game. He will be travelling with us to Liverpool."