"If this transaction is approved, it will give us the scale and reach to innovate and compete against our national and global competitors," Cohen told lawmakers on the Senate Judiciary Committee.
"The transaction will not lead to any reduction in competition or consumer choice in any market," he said. "While this transaction will make us bigger, that's a good thing, not a problem."
The Judiciary Committee is evaluating the proposed merger between the two cable giants to ensure it will not foster anto-competitive or monopolistic behavior.
Meanwhile, U.S. Senator Al Franken, who has in the past criticized Comcast's plan to buy Time Warner Cable but stopped short of asking for it to be blocked, expressed his opposition to the deal.
"I'm against this deal," he said. "I believe this deal will result in fewer choices, higher prices and even worse service for my constituents."
The Justice Department and the Federal Communications Commission must approve the merger for it to go forward.
U.S. Senator Patrick Leahy, chairman of the Senate Judiciary Committee, urged Comcast to support stronger, extended net neutrality rules.
Leahy noted that Comcast agreed to the rules as part of its 2011 deal to buy NBC Universal, and that the No. 1 cable company had reaffirmed its commitment to so-called network neutrality rules, which ban Internet providers from slowing down or blocking access to content online.
"The conditions that currently apply to Comcast should not be seen as the end point, but rather the minimum level of protection that should apply to promote competition online," said Leahy. "I urge Comcast to support stronger rules that will protect consumers and drive innovation."
Federal Communications Commission rules aimed at ensuring net neutrality were struck down in January but the agency is aiming to rewrite them.
--CNBC.com contributed to this story.