(Reuters) - Over 100 leading technology companies including Google Inc, Facebook Inc, Twitter Inc and Amazon.com Inc have written to U.S. telecom regulators to oppose a new "net neutrality" plan that would regulate how Internet providers manage web traffic.

The letter to Federal Communications Commission Chairman Tom Wheeler and the agency's four commissioners, warning of a "grave threat to the Internet," came amid calls for a delay in a vote on the plan scheduled for May 15.

"I believe that rushing headlong into a rulemaking next week fails to respect the public response to his (Wheeler's) proposal," FCC Commissioner Jessica Rosenworcel said on Wednesday in remarks prepared for delivery to an industry meeting.

Rosenworcel called for a delay of "at least a month" on Wheeler's plan.

With two Republican commissioners broadly opposed to regulation of Internet traffic, the support of two Democrats on the panel is critical.

In their letter, the technology and Internet companies, which ranged from household names to small startups, called on the FCC to "take the necessary steps to ensure that the Internet remains an open platform for speech and commerce."

Commission rules should not permit "individualized bargaining and discrimination," the companies said.

(Reporting by Alina Selyukh; Editing by Ros Krasny and Sandra Maler)