Federal Communications Commission Chairman Tom Wheeler walked a fine line Tuesday defending his controversial proposal to set up Internet "fast lanes," saying his agency could block such deals if they slowed down other traffic.

In an appearance before a Congressional committee, Wheeler acknowledged that a speedier Web highway for some would automatically mean other content was slower by comparison. But he said the FCC could swiftly move to block any arrangement that purposefully slowed down any traffic.

"That would be commercially unreasonable under our proposal," Wheeler said.

Wheeler’s appearance came just days after the commission voted 3 to 2 to move forward with proposed rules that would allow Internet providers to charge Web companies like Netflix for faster access to customers.

The proposed rules sparked a firestorm of criticism from advocates and tech companies who believe a so-called "two-lane Internet" would violate the popular notion of net neutrality, or the idea that all Web traffic should be treated equally.

Internet providers aren't happy about Wheeler's proposal either because it leaves open the possibility of tighter regulations of their services.

Wheeler told lawmakers his proposal was necessary because there are currently no rules in place that prevent Internet providers from blocking or slowing certain content. His proposal would prohibit that, he said.

“When customers buy access to the Internet they are buying access to the full Internet, and that's what our rules attempt to protect,” Wheeler said.

Wheeler insisted his proposal would not create a two-tiered Internet with "haves and have nots."

“I’ve consistently said there is only one Internet,” Wheeler said, pounding his hand on the table. “There is no 'fast Internet' and 'slow Internet'...There is one Internet."

At Tuesday's hearing, Democrats said they worried Wheeler's proposal to create an Internet fast lane would put smaller companies that can't afford to pay for access at a disadvantage.

"We could inadvertently block the next Google and Amazon from the market without knowing it," said Rep. Doris Matsui (D-Calif.).

Matsui called on Wheeler to ban so-called "paid prioritization" -- or deals that give Web companies faster access to customers for a fee.

Meanwhile, Republican lawmakers expressed concerns about part of Wheeler's proposal that asks whether the FCC should tighten regulations of Internet providers by reclassifying high-speed broadband as a utility.

"This policy would be an extreme example of government overreach," Rep. Bob Latta, a Republic from Ohio, said.

Wheeler largely avoided giving his opinion on questions like whether to increase oversight of Internet providers, saying his proposal asks the public to decide. "That's exactly the kind of question that we're asking," he said.