U.S. communications regulators adopted Internet traffic rules on Tuesday that prevent providers from blocking lawful content but still let them ration access to their networks.

The Federal Communications Commission approved the Open Internet order after FCC Chairman Julius Genachowski's plan got the support of fellow Democrats Michael Copps and Mignon Clyburn.

The rules aim to strike a balance between the interests of Web service providers, content companies and consumers, but some industry analysts think a court challenge is still likely.

At issue is whether regulators need to guarantee that all stakeholders continue to have reasonable access to the Internet, a principle often called net neutrality, or whether the Internet is best left to flourish unregulated.

The two Republican commissioners at the agency opposed the measure saying it was unnecessary and would stifle innovation. Robert McDowell and Meredith Attwell Baker told an FCC open meeting that they believed the rules would fail in court.

High-speed Internet providers like Comcast Corp and Verizon Communications can reasonably manage their networks under the rules and perhaps charge consumers based on levels of Internet usage.

The rules, to be somewhat looser for wireless Internet, could help cable companies in competition with plans by Microsoft Corp, Google Inc and Amazon.com to deliver competing video content over the same Internet lines the cable companies run to customers' homes.

(Reporting by Jasmin Melvin; Editing by Tim Dobbyn)