New England Patriots owner Robert Kraft has called the NFL's decision to uphold quarterback Tom Brady's four-game ban for deflategate "unfathomable".

The owner decided to address the issue before head coach Bill Belichick's press conference and took no questions after a short statement.

Kraft told reporters: "The decision handed down by the league yesterday is unfathomable to me.

"Six months removed from the AFC championship game, the league still has no hard evidence of anybody doing anything to tamper with the PSI levels of footballs.

"I continue to unequivocally support Tom Brady. I was wrong to put my faith in the league."

Kraft expressed his disappointment at the lengths the league was going to to hurt Brady's reputation, calling it "reprehensible".

The 74-year-old has also apologised to the Patriots' fan base, believing his decision to step aside in May would help absolve Brady but now saying that he was "wrong".