O'Leary made an inquiry about Viduka when Villa played at Leeds on Boxing Day and thinks he has a realistic chance of success because of United's financial problems.
O'Leary knows Leeds will have to consider offers, not least because Viduka's £65k-a-week wages are a large drain on a club which is more than £80m in debt.
Manchester United have also made an approach for Viduka but are interested in other targets.
Leeds will sell Viduka because the transfer fee may help satisfy the short-term demands of two of their major creditors before the January 19th deadline when they may face administration.
Villa's problem will be affording Viduka's wages as he is being paid almost three times the salary limit at the club.