Sen. Patrick Leahy (D-VT) today called on Comcast to make a long-term pledge that it won't charge content providers for faster access to its subscribers.

Comcast already agreed to follow network neutrality provisions until September 2018 as part of its 2011 purchase of NBCUniversal. While the agreement with the US government doesn't specifically prevent Comcast from signing paid prioritization deals, the company has said it has no plans to do so. Comcast has been touting its net neutrality commitments while making the case that it should be allowed to purchase Time Warner Cable, the second biggest cable company in the US after itself.

Leahy, chairman of the Senate Judiciary Committee, wrote a letter to Comcast Executive VP David Cohen today, saying he worries about "the risk of paid prioritization agreements through which websites could be charged for priority access over the Internet." Leahy wants "meaningful pledges from our Nation's broadband providers that they share the American public's commitment to an Internet that remains open and equally accessible to all."

"As a condition of the Comcast-NBC Universal merger, Comcast is bound to the net neutrality principles embodied in the FCC's Open Internet Order through the end of 2018," he wrote. "Those rules should be viewed as a minimum level of protection to promote competition online and Comcast's commitment to those principles should extend well beyond the imminent cut-off date of 2018. As the antitrust regulators continue to evaluate Comcast's proposed transaction with Time Warner Cable, and regardless of whether it is approved, I ask Comcast to pledge that it will not engage in paid prioritization. I also ask that Comcast pledge not to engage in any activity that prioritizes affiliated content or services over unaffiliated content or services, helping to ensure that vertical integration does not threaten competition online."

Comcast is reviewing the letter, a company spokesperson told Ars.

The Federal Communications Commission is considering whether to create net neutrality rules that ban paid prioritization. Leahy's letter to Comcast noted that he has "introduced legislation with Congresswoman Doris Matsui that would ban paid prioritization arrangements and has urged the FCC to enact meaningful net neutrality rules to preserve the Internet we know today."

Out of all major ISPs, Verizon may be the likeliest to offer paid fast lanes for Internet content providers. The company sued the FCC to overturn previous net neutrality rules issued in 2010, and Verizon said in court arguments that it would offer fast lanes if it's allowed to.

Comcast has been criticized for charging Netflix for a direct connection to the edge of its network, but that kind of arrangement isn't targeted by most net neutrality proposals. Generally, net neutrality rules focus only on whether traffic is prioritized after it enters the Internet service provider's network.

UPDATE: On Oct. 23, Leahy sent similar letters to AT&T, Verizon, Time Warner Cable, and Charter asking for commitments that they won't create paid Internet fast lanes.