Several influential figures responsible for creating the internet have demanded that a controversial vote be cancelled.
This week the Federal Communications Commission (FCC) will decide on whether to repeal an Obama-era law that protects "net neutrality".
It refers to the principle that all traffic on the internet is treated equally.
The pioneers said the FCC did not know what it was doing.
"It is important to understand that the FCC’s proposed Order is based on a flawed and factually inaccurate understanding of internet technology," the open letter read.
Signees included several of the architects of the early internet and world wide web, such as Vint Cerf and Sir Tim Berners-Lee, along with Steve Wozniak, the Apple co-founder.
The letter calls for the vote, due to be held on 14 December, to be cancelled due to what the authors regard as a lack of transparency and a refusal to listen to critics of the plan.
"The FCC’s rushed and technically incorrect proposed Order to abolish net neutrality protections without any replacement is an imminent threat to the internet we worked so hard to create," the letter states. "It should be stopped."
The letter, signed by 21 notable people, was sent to the Senate's commerce subcommittee on communications, technology, innovation and the internet.
This week could be pivotal in the history of the internet. Although it is yet to vote, there is no doubt that the Republican-controlled FCC will choose to end net neutrality when it makes its ruling on Thursday.
Without laws protecting the principles, campaigners say internet service providers (ISPs) will have free rein to exploit new power by throttling certain types of internet traffic.
For example, an ISP may decide to charge extra to use a service such as Netflix, or give a company an upper hand by not counting use of certain services when charging users for data bandwidth.
Such moves are theoretical, but until now were prevented by law.
The FCC believes the possible impact of the move has been exaggerated, and said the change in regulations would help improve competition and remove government meddling in the internet.
It said the open market should mean users are not unfairly treated by ISPs - despite many Americans only having one choice of provider in certain parts of the country.
In a move designed to allay fears of foul play, the FCC and Federal Trade Commission (FTC) on Monday announced new coordination to clamp down on unfair behaviour from telecoms companies.
The FCC and the FTC, the government body tasked with protecting consumer rights, will jointly investigate any issues.
"Instead of saddling the Internet with heavy-handed regulations, we will work together to take targeted action against bad actors," the FCC said.
The FCC's pledge reads that internet providers must be transparent in providing "information concerning an ISP’s practices with respect to blocking, throttling, paid prioritization, and congestion management".
That wording only seemed to intensify campaigners' fears.
Chris Lewis, from pro-net neutrality group Public Knowledge, said: "There is no comfort in this announcement from the FTC.
"Not only is the FCC eliminating basic net neutrality rules, but it’s joining forces with the FTC to say it will only act when a broadband provider is deceiving the public."
He added: "This gives free rein to broadband providers to block or throttle your broadband service as long as they inform you of it."
Protests against the FCC's move will step up a gear on Tuesday. Campaigners have pledged to "break the internet" with floods of messages urging people to contact their representatives.