Long-delayed U.S. Internet rules that tackle the controversial issue of balancing consumer and content provider interests against those who sell access to the Web will take effect November 20.

The Federal Communications Commission's open Internet order was published in the Federal Register on Friday, and immediately drew threats of court and congressional challenges.

The rules were adopted by the FCC late last year after a lengthy debate, but only recently cleared a review by the White House's Office of Management and Budget.

Criticized by opponents as a legally shaky government intrusion into regulating the Internet, the new rules forbid broadband providers from blocking legal content but leave flexibility for providers to manage their networks.

Broadband provider Verizon Communications Inc has been a vociferous opponent, and renewed its pledge to take the FCC to court as soon as the rules are published.

We have said all along that once we see the publication ... we intend to file another notice of appeal, Verizon spokesman Ed McFadden said.

For the past 10 years, the possibility of regulations to mandate the neutrality of the Internet -- in terms of restrictions on content, sites, platforms and types of equipment that may be attached -- has been the subject of fierce debate.

The latest rulemaking was prompted by a U.S. federal appeals court ruling last year that the FCC lacked the authority to stop Comcast Corp from blocking bandwidth-hogging applications on its broadband network.

The rules, adopted last December in a 3-2 vote, give the FCC power to ensure consumer access to huge movie files and other content while allowing Internet service providers to manage their networks to prevent congestion.

An FCC spokesman said the rules increase certainty and predictability, stimulating investment and ensuring job creation and economic growth.

But public interest groups criticized the rules as too weak, saying the FCC bent heavily to the will of big industry players including AT&T Inc and Comcast.

Matt Wood, policy director of public interest group Free Press, said broadband providers will be able to divide the Internet into fast and slow lanes and that the rules fail to protect mobile broadband users.

Even in their watered-down form, the rules might do some good -- but that would require a vigilant FCC to carefully monitor and address complaints, Wood said in a statement, adding that he doubted the agency would do enough to protect consumers.

While some public interest groups had considered a lawsuit to strengthen the rules, they now seem focused on ensuring the rules stay in place.

We are prepared to vigorously defend the FCC's rules in court and in Congress, said Gigi Sohn, president of Public Knowledge. She said the rules are a good start despite not being as strong as she had hoped.

The U.S. Court of Appeals for the District of Columbia Circuit in April threw out earlier challenges to the FCC's open Internet order by Verizon and MetroPCS Communications Inc, dismissing their lawsuits as premature.

FCC rulemakings generally cannot be challenged until the rules are published in the Federal Register.

Top Republican lawmakers vowed after the rules were adopted to find a way to reverse what they called an unprecedented power grab by the FCC, calling the rules unnecessary and misguided.

In order to turn back the FCC's onerous net neutrality restrictions, I will push for a Senate vote this fall on my resolution of disapproval, Senator Kay Bailey Hutchison, the ranking Republican on the Senate Commerce Committee, said in a statement on Friday.

The Republican-controlled House of Representatives pushed through a measure in April to overturn the order and prevent the FCC from adopting any rules related to it. The effort faces a tougher climb in the Senate, where Democrats retain a majority.

The White House has said President Barack Obama's advisers would recommend he veto any such resolution against the Internet rules if it were to make it to his desk.

(Reporting by Jasmin Melvin in Washington; Editing by Tim Dobbyn)