WASHINGTON >> Broadband providers sued the Federal Communications Commission to try to stop tough new net neutrality regulations, the first step in an expected lengthy court fight over the online traffic rules.

US Telecom, a trade group whose membership includes AT&T Inc. and Verizon Communications Inc., filed a petition Monday in the U.S. Court of Appeals for the District of Columbia Circuit.

The group wants the court to review the FCC’s rules because they are “arbitrary, capricious and an abuse of discretion” as well as a violation of existing law, according to the petition.

The regulations, passed by a 3-2 vote last month, are designed to ensure the uninhibited flow of Internet content. They prohibit broadband providers from blocking, slowing or selling faster delivery of legal content flowing through their networks to consumers.

Broadband firms oppose the FCC’s decision to classify high-speed Internet as a telecommunications service under Title 2 of the Communications Act, subjecting it to utility-like regulation.

FCC Chairman Tom Wheeler has promised a light-handed approach, but companies have complained that the rules will hinder investment and had indicated that lawsuits were likely.

“The focus of our legal appeal will be on the FCC’s decision to reclassify broadband Internet access service as a public utility service after a decade of amazing innovation and investment under the FCC’s previous light-touch approach,” said Jon Banks, US Telecom’s senior vice president.

“As our industry has said many times, we do not block or throttle traffic and FCC rules prohibiting blocking or throttling will not be the focus of our appeal,” he said.

A similar petition was filed in the U.S. Court of Appeals in New Orleans by Alamo Broadband Inc., an Elmendorf, Texas, Internet service provider. An attorney for Alamo did not respond to a phone message and email requesting comment.

Both petitions seek to preserve the right to file suit against the rules.

The petitions were filed Monday out of concern that when the FCC posted the final rules on its website March 12, a 10-day period to challenge them was triggered. The 10 days expired Sunday, meaning petitions would have to be filed by Monday.

But the FCC said the deadline for legal challenges is 60 days after the rules are published in the Federal Register. That publication is expected in the coming days.

An FCC spokesperson said the petitions filed Monday “are premature and subject to dismissal.”

Other legal challenges might also be filed. Verizon successfully sued to stop the FCC’s 2010 net neutrality regulations. The case took three years to decide.

“These companies have threatened all along to sue over the FCC’s decision, even though that decision is supported by millions of people and absolutely essential for our economy,” said Matt Wood, policy director of Free Press, a public interest group that supports the regulations.

“Apparently some of them couldn’t wait to make good on that threat,” he said.