Genachowski tried to allay some of those concerns. He said the rules would be enforced case by case. When networks are congested, for example, telecommunications companies might be allowed to limit use by "very heavy users" so other customers would still have access to the Internet.
Restrictions also might be applied differently to wireless than to cable or fiber-optic lines. He promised that the FCC would fully analyze the implications for wireless networks as it drafts detailed rules.
"This is not about government regulation of the Internet," Genachowski said. "It's about fair rules of the road for companies that control access to the Internet.
"The rise of serious challenges to the free and open Internet puts us at a crossroads. We could see the Internet's doors shut to entrepreneurs, the spirit of innovation stifled, a full and free flow of information compromised."
Obama was a strong supporter of network neutrality during the presidential campaign, helping to draw online support.
He praised the announcement Monday by Genachowski, a former Internet executive he appointed this year to head the FCC, as an important step "to preserve an open Internet in which all Americans can participate and benefit."
The FCC's four guiding Internet principles since 2005 assure that Internet users can access any legal content, application or service and allow them to attach any device to the Internet as long as it doesn't harm the network.
In addition to strengthening those principles, Genachowski's proposal would mandate that operators clearly state their policies.
Telecom trade groups said they were willing to work with the FCC on updating rules but cautioned about the risks of over-regulation.
Genachowski's proposals would have to be approved by the FCC. The five-member commission's other two Democrats, Michael J. Copps and Mignon Clyburn, said Monday they supported the plan, guaranteeing enough votes to pass it.
But the FCC's two Republican commissioners, Robert M. McDowell and Meredith A. Baker, said they were worried about the proposed new rules. In a joint statement, they called it "a dramatic proposal to grow government's involvement in Internet governance and management."
And some Senate Republicans backed an amendment to prohibit the FCC from enacting new rules.
"The Internet has flourished in large part because of a lack of government interference," Sen. John Ensign (R-Nev.) said. "I see no need to change that now."