Though they may be bros, Lil Wayne refuses to collaborate with Justin Bieber ... No matter how much he begs. He's got good intentions, of course. Weezy says he doesn't want to mess with the 'Baby' singer's squeaky-clean image.

Allegedly, the Biebs has been bugging not-so-Lil Wayne to do a duet with him, and he's even started pestering the most famous rapper through text message. Wayne says, with all due respect, hell naw.

"That's my little homie now," Weezy clarifies in a new interview with XXL Magazine. "He texts me every night asking me to do [his] d--- song. That's my n----, but I can't do it. Like I said, I don't want to f--- his sh-- up."

As of late, Biebs has been testing the tainted waters, sporting new tattoos and ear piercings, so maybe he doesn't want to be the pop-fresh, good boy he's been painted as. Still, Wayne doesn't want to exchange his own sharp lyrics for a toned down version, and we're not so sure the 'One Less Lonely Girl' pop star is quite ready for the dark side.

Anyway, Wayne has his sights set on another clean face. "I want to work with Justin Timberlake," he admits. "That boy got a voice; that boy can sing. He needs to come back right there on Tha Carter IV." At least, at 30, Timberlake is old enough to make his own decisions and work alongside the notoriously troublesome rapper -- without having to get a permission slip from his mom.

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