Sources close to the situation say Watkins is very interested in the prospect of moving to Saudi Arabia after Al Hilal made another approach for the England striker.
Villa have tried to prevent the move and would be willing to offer Watkins a new contract, but Al Hilal are showing persistence. The player's desire to make the move means a transfer is now considered likely to happen, sources told Flashscore.
Villa are aware they are facing a losing battle and have therefore accelerated their efforts to find a replacement, with Jackson emerging as their leading target.
A deal worth around £65 million would be required to satisfy Chelsea's demands for the forward.
Jackson is well known to Villa manager Unai Emery, who worked with him during their time together at Villarreal. The striker has also been coveted by Atletico Madrid this summer.
Villa are unhappy at the prospect of losing Watkins in the same window in which they have already sold Morgan Rogers, Youri Tielemans and Ezri Konsa.
However, they are determined not to be left short in attack and are moving quickly to bring Jackson in should Watkins' expected departure materialise.
The next few days could therefore see significant movement, with Watkins edging closer to the exit and Jackson potentially arriving as his replacement.