Alex Rodriguez -- If MLB Doesn't Fold On My Suspension ... I'LL SUE

Alex Rodriguez not only feels the MLB is singling him out ... he feels "persecuted" in the PED scandal -- and plans to SUE if the league doesn't COMPLETELY recant ... TMZ has learned.

Sources directly connected to A-Rod tell us he's prepared to march into Federal court next month ... unless the 211-game suspension the MLB slapped him with last week isn't entirely lifted.

The reason for A-Rod's bold demand -- A-Rod sources familiar with the investigation tell us Alex hasn't tested positive and never "knowingly" used PEDs since 2003 ... the last season he admitted using 'roids. Our sources say A-Rod has been drug tested 11 times between 2011 and the present ... and all of the results were negative.

Our sources fume it's "absurd" Ryan Braun -- who reportedly tested positive in 2011 and then lied about it -- was only benched for the duration of this season. They say it proves MLB's investigation of A-Rod and the Biogenesis Clinic has been "abusive and borderline illegal."

As for rumors A-Rod impeded baseball's PED investigation -- our sources say the league has "no proof" the Yankees slugger did any such thing, and further claim MLB is the one that has harassed and intimidated witnesses.

According to our sources, Alex will sue for various things, including a violation of the Collective Bargaining Agreement between the players' union and the league.

So, from 211 games to nothing ... or else.

Pretty big cojones for a guy accused of using steroids.