Justin Bieber's Doing President Obama a Favor

Justin Bieber's pretty much the most powerful tween on the planet -- and the most powerful grown man on the planet needs his help. Here's the deal: Last week President Obama told a 14-year-old girl whose father died in the 9/11 attacks that he "knows Justin" and could arrange for her to meet the heartthrob.

Apparently the White House phoned in the favor to the Bieb the very day President Obama met Payton Wall and he agreed!

Now Justin is making clear that he'll make good on Obama's promise, despite certain news outlets that say it'll never happen.

The Bieb tweeted to the naysayers: "I think you're wrong. Pretty sure President @BarackObama will keep this promise."

Sources tell TMZ Bieber is totally excited about making the girl's dream come true and told the White House he'll for sure meet the girl when he returns to the US and can make a trip to the East Coast. No date has been set yet.

Never say never, right?