WASHINGTON - The National Intelligence Estimate report identifies China as the country most aggressively seeking to penetrate the computer systems of American businesses and institutions to gain access to data that could be used for economic gain.

The report, which represents the consensus of the U.S. intelligence community, describes a range of sectors that have been the focus of hacking over the past five years: energy, finance, information technology, aerospace and automobiles, according to the individuals familiar with the report who spoke on the condition of anonymity.

The assessment does not quantify the financial impact of the espionage, but experts estimate it in the tens of billions of dollars.

COUNTERING THEFTS

Cyberespionage, which was once viewed as a concern mainly by U.S. intelligence and the military, is increasingly seen as a direct threat to the nation's economic interests.

In a sign of such concerns, the Obama administration is seeking ways to counter the online theft of trade secrets, according to officials. Analysts have said that the administration's options include formal protests, the expulsion of diplomatic personnel, the imposition of travel and visa restrictions, and complaints to the World Trade Organization.

Cyberespionage is "just so widespread that it's known to be a national issue at this point," said one administration official, who, like other current and former officials interviewed, spoke on the condition of anonymity.

EXPLOITING FAMILY TIES

The National Intelligence Estimate names three other countries - Russia, Israel and France - as having engaged in hacking for economic intelligence but makes clear that cyberespionage by those countries pales in comparison with China's effort.

China has staunchly rejected such allegations, saying the Beijing government neither condones nor carries out computer hacking.

At least as far back as the early 1980s, China has made the acquisition of Western technology - through means licit and illicit - a centerpiece of its economic development planning. The explosion in computer use has greatly aided that transfer of technology.

China's intelligence services and private companies frequently seek to exploit Chinese citizens or people with family ties to China who can use their insider access to U.S. corporate networks to steal trade secrets. A report by the Office of the National Counterintelligence Executive said they use thumb drives or email to gain access to trade information.

The National Intelligence Estimate comes at a time when the U.S. government is making a determined effort to develop policies that address cyberthreats against the nation.

"We need the NIE on cyber for a systematic and comprehensive understanding of what the most dangerous technologies are, who are the most threatening actors and what are our greatest vulnerabilities," said former deputy defense secretary William Lynn, who requested the report in 2011 but has not seen or been briefed on the contents.

Some officials have pressed for an unclassified summary to be released publicly. Michael Birmingham, a spokesman for the Office of the Director of National Intelligence, declined to comment on the report, except to say that "as a matter of policy, we do not discuss or acknowledge the existence of NIEs unless directed to do so."

Much of China's cyberespionage is thought to be directed at commercial targets linked to military technology. In 2011, when Chinese hackers attacked the network security company RSA Security, the technology stolen was used to penetrate military-industrial targets. Shortly after, the networks of defense contracting giant Lockheed Martin, which used RSA security tokens, were penetrated by Chinese hackers. The company said no data were taken.

Companies in other sectors also have been targeted, though the reasons for the espionage are not always related to economic interests. The New York Times, the Wall Street Journal and The Washington Post recently disclosed that they believe their networks were compromised in intrusions that originated in China.

GOOGLE ATTACKED

A watershed moment came in January 2010 when the tech titan Google announced that its networks had been hacked and that the intrusions originated in China. The intruders made off with valuable source code and targeted the Gmail accounts of Chinese human rights activists and dissidents, the company announced.

In a new book, Google chief executive Eric Schmidt says China is the world's "most sophisticated and prolific" hacker, adding: "It's fair to say we're already living in an age of state-led cyberwar, even if most of us aren't aware of it."