UPDATE 1-U.S. Federal Communications Commission set to reverse net neutrality rules

rules@ (Adds protest in front of FCC)

WASHINGTON, Dec 14 (Reuters) - The U.S. Federal Communications Commission is expected on Thursday to rescind rules that were aimed at ensuring a free and open internet, as protesters gathered online and in front of FCC headquarters to oppose the change.

Commission Chairman Ajit Pai's proposal marks a victory for big internet service providers such as AT&T Inc, Comcast Corp and Verizon Communications Inc that opposed the regulations - popularly known as net neutrality rules - and gives them sweeping powers to decide what web content consumers can access.

The move is opposed by Democrats, Hollywood and big internet companies like Google parent Alphabet Inc and Facebook Inc, which had urged Pai not to rescind the rules. The rules bar broadband service providers from blocking or slowing access to content, or charging consumers more for certain content.

Once repealed, several state attorneys general have said they will work to oppose the FCC ruling, citing problems with comments made to the FCC during the public comment period. Other critics have said they will consider challenging what they consider to be weaker enforcement.

Online protesters included celebrities like "Star Wars" actor Mark Hamill, while net neutrality supporters rallied in front of the FCC building in Washington ahead of the vote. Some Congress members were expected to attend the Washington protest before the vote.

The 2015 rules were intended to give consumers equal access to web content and prevent broadband providers from favoring their own content. Pai proposes allowing those practices as long as they are disclosed.

Michael Powell, a former FCC chairman who heads a trade group representing major cable companies and broadcasters, told reporters earlier in the week that internet providers would not block content because it would not make economic sense and consumers would not stand for it.

"They make a lot of money on an open internet," Powell said, adding it is "much more profitable" than a closed system. "This is not a pledge of good-heartedness, it's a pledge in the shareholders' interest."

A University of Maryland poll released this week found that more than 80 percent of respondents opposed the proposal. The survey of 1,077 registered voters was conducted online by the Program for Public Consultation at the University of Maryland from Dec. 6-8.

Democrats have said the absence of rules would be unacceptable and that they would work to overturn the proposal if it is approved. Advocates of the net neutrality rules also plan a legal challenge.

Pai's proposal is "like letting the bullies develop their own playground rules," said Democratic Senator Ed Markey.

Many Republicans back Pai's proposal but want Congress to write net neutrality rules. Senate Majority Leader Mitch McConnell said the FCC would "return the internet to a consumer-driven marketplace free of innovation-stifling regulations."

A group of nearly 20 state attorneys general asked the FCC to delay the vote until the issue of fake comments is addressed.

(Reporting by David Shepardson; Editing by Chris Sanders and Jonathan Oatis)