WASHINGTON (Reuters) -A U.S. appeals court on Thursday blocked the Federal Communications Commission's reinstatement of landmark net neutrality rules, saying broadband providers are likely to succeed in a legal challenge.

The FCC voted in April along party lines to reassume regulatory oversight of broadband internet and reinstate open internet rules adopted in 2015 that were rescinded under then-President Donald Trump.

The Sixth Circuit U.S. Court of Appeals, which had temporarily delayed the rules, said on Thursday it would temporarily block net neutrality rules and scheduled oral arguments for late October or early November on the issue, dealing a serious blow to President Joe Biden's effort to reinstate the rules.

"The final rule implicates a major question, and the commission has failed to satisfy the high bar for imposing such regulations," the court wrote. "Net neutrality is likely a major question requiring clear congressional authorization."

The court on July 12 had temporarily placed the net neutrality rules on hold until Aug. 5 as it considered industry legal challenges.

FCC Chair Jessica Rosenworcel said: "The American public wants an internet that is fast, open, and fair. Today's decision by the Sixth Circuit is a setback but we will not give up the fight for net neutrality."

Net neutrality rules require internet service providers to treat internet data and users equally rather than restricting access, slowing speeds or blocking content for certain users. The rules also forbid special arrangements in which ISPs give improved network speeds or access to favored users.

The rules would bar internet service providers from blocking or slowing down traffic to certain websites, or engaging in paid prioritization of lawful content, as well as give the FCC new tools to crack down on Chinese telecom companies and the ability to monitor internet service outages.

Reinstating net neutrality has been a priority for Biden, who signed a July 2021 executive order encouraging the FCC to reinstate the rules adopted in 2015 under President Barack Obama, a fellow Democrat.

Under Trump, the FCC had argued that net neutrality rules were unnecessary, blocked innovation and resulted in a decline in network investment by internet service providers, a contention disputed by Democrats.