WASHINGTON - Cyberattacks and cyberespionage pose a greater potential danger to U.S. national security than al-Qaida and other militants that have dominated America's global focus since Sept. 11, 2001, the nation's top intelligence officials said Tuesday.

For the first time, the growing risk of computer-launched foreign assaults on U.S. infrastructure, including the power grid and financial networks, was ranked higher in the U.S. intelligence community's annual review of worldwide threats than worries about terrorism, transnational organized crime and proliferation of weapons of mass destruction.

The startling reappraisal comes a day after President Obama's national security adviser, Tom Donilon, complained of "cyberintrusions emanating from China on an unprecedented scale" and said China-based digital attacks on U.S. businesses and institutions had become "a key point of concern."

"The international community cannot afford to tolerate such activity from any country," he warned in a speech at The Asia Society in New York.

Appearing Tuesday before the Senate intelligence committee, James Clapper, director of national security, said Russia and China are unlikely to launch a devastating cyberattack against the U.S. outside of a military conflict or crisis that they believe threatens their vital interests. But according to Clapper's written statement, computer hackers or organized groups "could access some poorly protected U.S. networks that control core functions, such as power generation" although their ability to cause "high-impact, systemic disruptions will probably be limited."