Club officials are making no comment but sources close to Villa are optimistic a deal may even be completed ahead of tonight's Europa League second leg qualifier with Rapid Vienna.
Warnock has been amongst manager martin O'Neill's main targets during a summer in which his net spending so far has only been around £6million.
He splashed out £21million for Stewart Downing, Fabian Delph and Habib Beye but recouped around £15million from the sale of Gareth Barry and Zat Knight.
Bolstering the back four has been O'Neill's priority since the retirement of Martin Laursen and selling Knight to Bolton and with Wilfred Bouma still not ready to return after a year-long injury lay-off.
Portsmouth's Sylvain Distin - also a target for Everton - and Manchester City's Richard Dunne are amongst his other targets.
Warnock has played more than 100 games for Blackburn since his move from Liverpool in 2007.
Transfer Specials. Click here to bet.