President Biden‘s annoucement Sunday that he was pardoning his son Hunter was nothing close to a spur of the moment decision … TMZ has learned.

White House-connected sources with direct knowledge tell TMZ … Biden had this planned for more than three months.

Our sources say President Biden was not involved in Hunter’s case in any way until June of last year, when a plea deal was rejected by the judge. We’re told he was “agitated” at the reversal and felt his son had become a political pawn.

As you know, Hunter was convicted on three gun-related charges this past June.

Now here’s the twist … we’re told Hunter and his legal team felt the second trial — where he was charged with 9 tax-related charges — was winnable. Yet Hunter entered a guilty plea in September, which at the time was puzzling because he and his lawyers felt they’d get a not guilty verdict.

Our sources — again, with direct knowledge — tell TMZ when the guilty verdict was entered it was done with knowledge that President Biden would pardon him.

Biden made good on his plans Sunday, when he pardoned his son … and said he felt the legal system was being politicized against Hunter.

The prez wrote in the press release that other people convicted of similar crimes to Hunter would have received non-criminal resolutions — but, Hunter was treated differently … all because of his relation to Joe.