WASHINGTON -- The Obama administration on Monday explicitly accused China's military of mounting attacks on American government computer systems and defense contractors, saying one motive could be to map "military capabilities that could be exploited during a crisis."
While some recent estimates have more than 90 percent of cyberespionage in the United States originating in China, the accusations relayed in the Pentagon's annual report to Congress on Chinese military capabilities were remarkable in their directness. Until now the administration avoided directly accusing both the Chinese government and the People's Liberation Army of using cyberweapons against the United States in a deliberate, government-developed strategy to steal intellectual property and gain strategic advantage.
"In 2012, numerous computer systems around the world, including those owned by the U.S. government, continued to be targeted for intrusions, some of which appear to be attributable directly to the Chinese government and military," the nearly 100-page report said.
The report, released Monday, described China's primary goal as stealing industrial technology, but said many intrusions also seemed aimed at obtaining insights into American policy makers' thinking. It warned that the same information-gathering could easily be used for "building a picture of U.S. network defense networks, logistics, and related military capabilities that could be exploited during a crisis."
It was unclear why the administration chose the Pentagon report to make assertions that it has long declined to make at the White House. A White House official declined to say at what level the report was cleared. A senior defense official said "this was a thoroughly coordinated report," but did not elaborate.
On Tuesday, a spokeswoman for the Chinese Ministry of Foreign Affairs, Hua Chunying, criticized the report.
''China has repeatedly said that we resolutely oppose all forms of hacker attacks,'' she said. ''We're willing to carry out an even-tempered and constructive dialogue with the U.S. on the issue of Internet security. But we are firmly opposed to any groundless accusations and speculations, since they will only damage the cooperation efforts and atmosphere between the two sides to strengthen dialogue and cooperation.''
Missing from the Pentagon report was any acknowledgment of the similar abilities being developed in the United States, where billions of dollars are spent each year on cyberdefense and constructing increasingly sophisticated cyberweapons. Recently the director of the National Security Agency, Gen. Keith Alexander, who is also commander of the military's fast-growing Cyber Command, told Congress that he was creating more than a dozen offensive cyberunits, designed to mount attacks, when necessary, at foreign computer networks.
When the United States mounted its cyberattacks on Iran's nuclear facilities early in President Obama's first term, Mr. Obama expressed concern to aides that China and other states might use the American operations to justify their own intrusions.
But the Pentagon report describes something far more sophisticated: a China that has now leapt into the first ranks of offensive cybertechnologies. It is investing in electronic warfare capabilities in an effort to blind American satellites and other space assets, and hopes to use electronic and traditional weapons systems to gradually push the United States military presence into the mid-Pacific nearly 2,000 miles from China's coast.
The report argues that China's first aircraft carrier, the Liaoning, commissioned last September, is the first of several carriers the country plans to deploy over the next 15 years. It said the carrier would not reach "operational effectiveness" for three or four years, but is already set to operate in the East and South China Seas, the site of China's territorial disputes with several neighbors, including Japan, Indonesia, the Philippines and Vietnam. The report notes a new carrier base under construction in Yuchi.
The report also detailed China's progress in developing its stealth aircraft, first tested in January 2011.
Three months ago the Obama administration would not officially confirm reports in The New York Times, based in large part on a detailed study by the computer security firm Mandiant, that identified P.L.A. Unit 61398 near Shanghai as the likely source of many of the biggest thefts of data from American companies and some government institutions.
Until Monday, the strongest critique of China had come from Thomas E. Donilon, the president's national security adviser, who said in a speech at the Asia Society in March that American companies were increasingly concerned about "cyberintrusions emanating from China on an unprecedented scale," and that "the international community cannot tolerate such activity from any country." He stopped short of blaming the Chinese government for the espionage.
But government officials said the overall issue of cyberintrusions would move to the center of the United States-China relationship, and it was raised on recent trips to Beijing by Treasury Secretary Jacob J. Lew and the chairman of the Joint Chiefs of Staff, Gen. Martin E. Dempsey.
To bolster its case, the report argues that cyberweapons have become integral to Chinese military strategy. It cites two major public works of military doctrine, "Science of Strategy" and "Science of Campaigns," saying they identify "information warfare (I.W.) as integral to achieving information superiority and an effective means for countering a stronger foe." But it notes that neither document "identifies the specific criteria for employing a computer network attack against an adversary," though they "advocate developing capabilities to compete in this medium."
It is a critique the Chinese could easily level at the United States, where the Pentagon has declined to describe the conditions under which it would use offensive cyberweapons. The Iran operation was considered a covert action, run by intelligence agencies, though many techniques used to manipulate Iran's computer controllers would be common to a military program.
The Pentagon report also explicitly states that China's investments in the United States aim to bolster its own military technology. "China continues to leverage foreign investments, commercial joint ventures, academic exchanges, the experience of repatriated Chinese students and researchers, and state-sponsored industrial and technical espionage to increase the level of technologies and expertise available to support military research, development and acquisition."
But the report does not address how the Obama administration should deal with that problem in an economically interconnected world where the United States encourages those investments, and its own in China, to create jobs and deepen the relationship between the world's No. 1 and No. 2 economies. Some experts have argued that the threat from China has been exaggerated. They point out that the Chinese government -- unlike, say, Iran or North Korea -- has such deep investments in the United States that it cannot afford to mount a crippling cyberstrike on the country.
The report estimates that China's defense budget is $135 billion to $215 billion, a large range attributable in part to the opaqueness of Chinese budgeting. While the figure is huge in Asia, the top estimate would still be less than a third of what the United States spends every year.
Some of the report's most interesting elements examine the debate inside China over whether this is a moment for the country to bide its time, focusing on internal challenges, or to directly challenge the United States and other powers in the Pacific.
But it said that "proponents of a more active and assertive Chinese role on the world stage" -- a group whose members it did not name -- "have suggested that China would be better served by a firm stance in the face of U.S. or other regional pressure."
Correction: May 7, 2013, Tuesday
This article has been revised to reflect the following correction: An earlier version of this article misstated the number of the unit identified by a New York Times article in February as the likely source of many of the biggest thefts of data from American companies and some government institutions. It is P.L.A. Unit 61398, not 21398. The article also misspelled the name of China's first aircraft carrier. It is the Liaoning, not the Lianoning.
This article originally appeared in The New York Times.