Comcast Corp (NASDAQ: CMCSA). and Charter Communications (NASDAQ: CHTR) have reached an operational agreement on working together on wireless communications plans, a source close to the efforts told CNBC on Sunday.

Under the agreement, Comcast will only sell wireless to its customers and Charter will only sell wireless to its customers.

The two companies also reached an agreement in which Comcast and Charter will only work together to approach any of the major wireless companies about MVNO (mobile virtual network operators) deals. They also agreed that neither company will enter into any material transaction independently without consent from the other pending a year notice.

A formal announcement has not yet been made.

Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.

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