WASHINGTON — The nation’s top regulator of telecommunications networks said Monday he will push for formal rules to protect the Internet from discriminatory practices that could block consumers from accessing certain Web sites or services.

Julius Genachowski, chairman of the Federal Communications Commission, said a free and open Internet remains critical to the future growth of the U.S. economy. He plans to circulate his proposal soon among the FCC’s five commissioners and hold public hearings later this year.

The Republican-led FCC adopted four principles in 2005 designed to keep the Internet open. Genachowski, a Democrat chosen by President Barack Obama, wants to turn the FCC’s principles into concrete rules and add two more. That would give additional legal muscle to the enforcement of the agency’s rules.

The debate over how to regulate the Internet _ an issue known as “Net neutrality” _ has simmered in Washington for the past decade. So far there have been few instances of major violations, but Genachowski warned that “we’re seeing the breaks and cracks emerge.” Most notably, cable giant Comcast Corp. was discovered last year to be secretly blocking some large file transfers between users.

“We need to think about the networks we need today as well as the networks we’ll need tomorrow,” Obama said during a speech in upstate New York after Genachowski’s initiative was unveiled.

One of the new rules proposed by Genachowski would bar owners of both wireless and wireline networks from blocking access to any Web site or application, including services that compete with their own, except in very limited circumstances. Wireless has been excluded from the FCC’s Internet-protection oversight.

“It is essential that the Internet remain open, however users reach it,” Genachowski said in a speech Monday at the Brookings Institution.

The FCC would continue to allow operators to institute “reasonable” rules to manage their networks to protect against spam, fraud, congestion or other problems.

Yet another proposal by Genachowski would force operators to clearly disclose their network-management practices.

The FCC chairman left open the possibility that network operators could sell enhanced Internet services to customers willing to pay more, so long as “ample” speed and bandwidth is available for other consumers and businesses.

Genachowski also emphasized the FCC would not overstep its bounds. Citing his experience as a media executive and high-tech investor, he acknowledged that excessive rules could crimp innovation and investment.

“This is not about government regulation of the Internet,” he said. Some of the nation’s largest network operators _ and gatekeepers _ of the Internet include AT&T Inc., Verizon Communications Inc. and Comcast.

David Young, a senior Verizon executive based in Washington, said his company supported an open Internet, but he expressed concern that new FCC rules could cause harmful unintended consequences.

Arguing that the Internet has grown rapidly with minimal regulation, Young said: “I truly don’t understand what the problem is we’re trying to solve.”

Yet Ben Scott of Free Press, a consumer-advocacy group, said greater regulatory scrutiny is necessary to prevent similar incidents like the one involving Comcast. He applauded Genachowski’s call for formal rules and said it would be good for both consumers and businesses.

“This is not something we should be wary of or frightened about,” he said. 

• Jeffry Bartash