He said that the deal with Verizon was "reached swiftly and amicably in just a few days after our conversations began." But he offered little hope that an agreement with Time Warner is in sight.
"I cannot describe to you the frustration I feel at the way these negotiations have gone," Moonves wrote. "Never in my most pessimistic moments did I ever think that they would have lasted this long and have been so difficult."
He claimed Time Warner is demanding "different terms than any other company in the business."
"I am frankly mystified by what appears to be a lack of urgency to resolve this matter for their customers," he said, adding that he is still prepared to negotiate with Time Warner.
The cable company has accused CBS of demanding an exorbitant rate increase and argues it is only fighting for a fair deal for its customers.
Time Warner and other cable companies have urged the Federal Communications Commission to intervene in the dispute to pressure CBS to accept a deal. Because CBS stations use the public airwaves, they are required to act in the public's interest.
CBS has also taken fire from consumer advocacy groups for blocking access to its online videos for Time Warner broadband subscribers.
Lawmakers and regulators have urged the two companies to reach an agreement.