WASHINGTON – The Senate on Thursday fell short of passing legislation to protect the U.S. electrical grid, water supplies and critical industries from cyberattack and electronic espionage despite national security officials’ warnings about the potential for devastating assaults on American computer networks.

Republicans and Democrats said they are committed to approving a final bill when they return in September from a month-long recess. But deep divisions between the parties over the right approach to cybersecurity will make it difficult to forge a compromise.

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Sen. Susan Collins

Sen. Olympia Snowe

Sen. Susan Collins, a Maine Republican and one of the primary architects of the cybersecurity bill, called Thursday “a shameful day” and rebuked her colleagues, saying that “rarely have I been so disappointed in the Senate’s failure to come to grips with the threat to our country.”

“There is certainly plenty of blame to go around,” Collins said in a press conference after the “motion to proceed” on the bill failed on a 52-46 vote. “I cannot think of another area where the threat is greater and we are less prepared.”

The bill is intended to strengthen protections of the nation’s “critical infrastructure” — such as the electric grid, communications networks and financial systems — against attacks by hackers, organized crime or other nations. Top defense and security officials have warned that a major cyberattack could cause havoc.

Thursday’s vote was not entirely along party lines. Five Republicans — including Maine’s Sen. Olympia Snowe — joined 45 Democrats and the chamber’s two independents in support of the bill. However, several Democrats voted with the majority of Republicans to block consideration of the legislation.

The White House and Senate Democrats blamed Republicans for blocking what they called the only comprehensive piece of cybersecurity legislation that would have given the federal government and businesses the tools they need to deal with vulnerabilities in critical infrastructure systems.

More than 80 percent of the nation’s critical infrastructure is owned and operated by the private sector.

During Thursday’s floor debate, Democrats singled out the U.S. Chamber of Commerce for continuing to oppose the bill even after the authors rewrote significant portions in an attempt to win the support of the business community.

Those changes, most notably a switch from mandatory compliance with security standards to a voluntary system, were also criticized by some who viewed them as removing any teeth from the bill.

Failure to approve the Senate’s Cybersecurity Act of 2012 before the congressional recess amounted to a rejection of the advice from senior national security officials, including Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, who have been calling for Congress to act now on comprehensive legislation to deal with cyberthreats.

“The uncomfortable reality of our world today is that bits and bytes can be as threatening as bullets and bombs,” Dempsey said in a letter to Sen. Jay Rockefeller, D-W.Va.

But Republicans argued the bill would have led to regulations imposed by Washington that would only increase the private sector’s costs without substantially reducing its risks. They also said Democrats, who control the Senate, tried to ram the bill through without adequate time for debate.

Collins, who crafted the bill with independent Sen. Joseph Lieberman of Connecticut and several Democrats, blamed both parties for attempting to attach irrelevant amendments to the bill on the Senate floor. Senate Majority Leader Harry Reid, D-Nev., eventually shut down the amendment process, angering Republican leaders.

Congress is scheduled to go on its August recess at the end of this week and won’t return until after Labor Day.

Washington Bureau Chief Kevin Miller contributed to this report.