President Obama, at his final press conference in office, on Wednesday defended his controversial decision to commute the bulk of Chelsea Manning's 35-year prison sentence for leaking classified documents -- claiming the former Army intelligence analyst served a "tough" sentence, and disputing the notion that clemency could embolden future leakers.

"I feel very comfortable that justice has been served and that a message has still been sent," the president said.

The president has faced mounting bipartisan criticism over the commutation, announced as part of a wave of clemency decisions a day earlier. Manning, who has served more than six years of the 35-year sentence, will now be released in May.

To detractors warning the decision set a dangerous precedent, the president pushed back.  

"Chelsea Manning has served a tough prison sentence, so the notion that the average person who is thinking about disclosing vital classified information would think that it goes unpunished, I dont think would get that impression from the sentence that Chelsea Manning has served," Obama said.

Citing the time served and saying Manning's sentence was "disproportionate," Obama said: "It made sense to commute, and not pardon, her sentencing."