Microsoft revealed today that it has sued Samsung (PDF) in an attempt to enforce a patent cross-licensing agreement the two companies reached in 2011.

By Microsoft’s account, Samsung is balking at licensing fees after its smartphones became more successful than expected. The lawsuit alleges Samsung was late in paying its second-year royalties and then refused to pay interest. Microsoft’s acquisition of Nokia appears to be the reason that Samsung cited for not having to pay. With the lawsuit, Microsoft hopes that the court will enforce the contract.

We’ve reached out to Samsung for comment on the issue.

Microsoft spent years leveraging its patent portfolio against Android phone makers, eventually earning royalties from most of Google’s best partners.

Microsoft’s Samsung action [Microsoft on the Issues blog]

Image credit: Jon Russell / Flickr