Sprint has informed NASCAR it will not extend title sponsorship of the top Sprint Cup Series beyond its current contract, which expires after the 2016 season.

Sprint has been the entitlement sponsor for NASCAR's top series since 2004, when Nextel signed a 10-year agreement for the Nextel Cup Series. The name changed to the Sprint Cup Series in 2008 following the corporate merger between Nextel and Sprint corporate merger.

Sprint agreed to a three-year extension that took the contract through 2016.

Now, the company is citing "a need to focus more directly on its core business priorities," in ending its relationship with NASCAR.

NASCAR chief communications officer Brett Jewkes says the series understands that significant changes within Sprint led to the decision.