Pressure is building on US regulators to stop powerful firms from hogging Internet "fast lanes" that could be allowed under proposed rules that will be discussed next week.

More than 100 technology firms including titans Microsoft, Google, Facebook, and Twitter came out Wednesday against Federal Communications Commission (FCC) suggested rules of the road that seemingly run counter to the cherished ideal of "net neutrality."

Internet service providers with virtual strangleholds on some US cities would be able to charge tolls for data to get priority in "fast lanes" under regulations recommended by FCC chief Tom Wheeler last month.

Such rules "would enable phone and cable Internet service providers to discriminate both technically and financially against Internet companies and to impose new tolls on them," Google, Amazon, Microsoft and other Internet firms said in a letter to the FCC.

"This represents a grave threat to the Internet."

- Call to stall vote -

An FCC commissioner has called for a delay of the planned May 15 vote on the proposed rules in order to discuss making them stronger.

The rules wouldn't prevent ISPs from allowing tech titans such as Netflix or Google to pay for faster data speeds but would require that competing traffic move at "reasonable" speeds.

The "open Internet notice of proposed rule making" sent from Wheeler to the full commission last month was pounced on by critics as a betrayal of the goal of keeping the Internet "neutral" by preventing some online traffic from getting priority over other content.

Netflix came out against the notion of allowing toll-based fast lanes shortly after the proposal went public.

- Gap in oversight -

The FCC was adamant that it remains committed to net neutrality and is trying to create rules that can withstand legal scrutiny.

Two prior attempts, the most recent in 2010, by the FCC to hold broadband service providers to standards were stymied by US District Court decisions that such moves were outside the agency's scope of authority.

Wheeler seized on part of the most recent court decision that suggests the FCC has power to take action if ISPs act in "commercially unreasonable" ways.

The proposed rules "follow the roadmap established by the court as to how to enforce rules of the road that protect an open Internet," Wheeler said in a blog post.

"To be very direct, the proposal would establish that behavior harmful to consumers or competition by limiting the openness of the Internet will not be permitted," the FCC chairman maintained.

The FCC contends there is a "gap" in oversight of ISPs because the court struck down its efforts to ban blocking or slowing of online data.

Wheeler wants new rules in place by the end of this year.

The FCC maintained that the proposed rules will bar ISP behaviors "harmful to consumers" and allow it to set high standards for what is "commercially reasonable."

Net neutrality advocates argue that letting Internet firms with deep pockets pay for faster data transmission will put innovative young startups at a disadvantage.