Peter Kafka over at All Things Digital reports that Apple has yet another hurdle to overcome before iTunes cloud streaming can become a reality -- getting music publishers to sign off. Although Apple has been negotiating and finalizing deals with the music labels, including Sony now, that's apparently not enou.

While Apple came to terms with Warner Music and EMI Music weeks ago, and has now struck a deal with Sony Music, industry sources tell me the company doesn’t have agreements with the labels’ associated publishing companies–Warner/Chappell, EMI Music Publishing and Sony/ATV. The deal Apple is about to sign with Universal also won’t include publishing, I’m told.

Kafka explains how labels and publishers alike both receive compensation from digital sales, which is why Apple needs to take additional steps for securing deals with publishers before going live.

According to the report, this additional obstacle shouldn't have any real impact on Apple rolling out their cloud streaming service -- which is suspected to be announced at WWDC alongside iOS 5 -- because labels and publishers are essentially on the same page. Apple simply started negotiations with the labels first because those agreements were considered to be the more difficult arrangements to secure over publisher contracts.

Do you think Apple will have any trouble getting publishers to agree? Let us know what you think in the comments!