WASHINGTON — The Senate could leave town this week for a monthlong break without passing legislation to protect the U.S. electrical grid, water supplies and other critical industries from cyberattack and electronic espionage.

Congressional sponsors of the bill scrambled Wednesday to overcome Republican resistance to the measure, but they appeared short of the votes needed for passage despite dire warnings from top national security officials about the potential for devastating assaults on the computer networks that control the country's essential infrastructure.

President Barack Obama urged lawmakers to pass the legislation as soon as possible.