The Trump administration announced on Thursday that it would sharply restrict exports of civilian nuclear technology to China that officials claimed was being diverted to power new generations of Chinese submarines, aircraft carriers and floating nuclear power plants.
The announcement mixed security warnings with longstanding complaints that Beijing was continuing to steal nuclear-related technology from American firms to benefit Chinese state-owned companies.
In a call with reporters, however, administration officials revealed little of the intelligence evidence that they said would back up their claims.
The move appeared to be part of a more concerted effort by the administration to put new pressure on China beyond the tariffs that President Trump has announced on Chinese goods.
On Wednesday, the Trump administration said it would impose a new review system on foreign investments to prevent adversaries — chiefly China — from obtaining new technology by taking minority stakes in American companies or starting joint ventures here.
Also on Wednesday, the Justice Department announced the arrest of a Chinese intelligence officer who was charged with stealing secret information from GE Aviation, one of the largest suppliers of jet engines.
China has been an established nuclear weapons state since the early 1960s. While the Trump administration said it was acting to halt proliferation, the reality is that China is largely self-sufficient when it comes to developing nuclear weapons.
The restrictions announced on Thursday appeared largely aimed at fears that advanced reactors, especially compact power plants that could fuel China’s ambitions to project power, would speed the emergence of the Chinese military as a force with global reach.
The administration officials, who briefed journalists on the condition of anonymity, said Beijing was looking in particular to develop floating nuclear power reactors for use in the South China Sea, where it is building military instillations on reclaimed reefs.
China is not a major customer for American nuclear technology; only about $170 million in nuclear-related sales went to Chinese customers last year. But the announcement on Thursday amounted to a significant setback in cooperative agreements that have had a checkered history since the Reagan administration.
The first openings, noted Jeffrey A. Bader, the senior Asia specialist on President Barack Obama’s National Security Council, came as an incentive to stop Chinese cooperation with Pakistan, which was building its first nuclear weapons. Trade stopped after the Tiananmen Square uprising of 1989, and the Clinton administration had a major standoff with the Chinese over their help to Iran.
But those issues were resolved, usually amid warnings from the American nuclear industry that failing to deal with China on nuclear issues was to open the way for France, Japan and South Korea to supply Beijing with nuclear technology. But today, Mr. Bader noted, “there is not much left in the American nuclear industry to harm, so the administration can indulge their most extreme-case suspicions.”
There is little question that the Chinese have sought to steal nuclear-related technology: The United States has indicted Chinese hackers and insiders in a variety of cases that involved nuclear technology.
Last year, Szuhsiung Ho, an American citizen born in Taiwan, was sentenced to two years in prison for organizing American nuclear experts to help China develop nuclear materials. That indictment named the China General Nuclear Power Company, the largest Chinese nuclear producer, which was seeking American designs for key components for nuclear reactors.
The officials who briefed reporters, who came from three separate United States agencies with oversight of nuclear materials and technology, cited that case and others like it as they explained a new policy under which there would be a “presumption of denial” for Chinese licenses for certain advanced nuclear technologies. Older-style reactors, and common nuclear-related components, especially those widely available on global markets, will not be subject to the new restrictions.
In a speech in July, Christopher Ford, the senior State Department official for nuclear issues, said that the “hard question” in dealing with China is to what extent the United States can participate in its growing nuclear market “without providing China with technological tools that will help it achieve its goal of seizing a geopolitical role for itself that displaces U.S. influence.”
The administration said little on Thursday about how it pursued those goals. But the officials said that the new rules were based on a study conducted by the National Security Council that began last year, with heavy participation from intelligence agencies. But they would not say what intelligence findings, if any, justified the new restrictions.
In the past, intelligence officials have noted that since China is already a nuclear-weapons state, denying the country nuclear technology made relatively little sense on national security grounds, unless there was a significant risk of proliferation.
So instead, the administration based its decision, the officials said, on concerns about helping China extend the reach of its fleets — like nuclear-powered icebreakers or floating power plants that could be used to solidify China’s presence in the South China Sea, where it has claimed exclusive jurisdiction in areas around reefs that it reclaimed.
Despite promises from President Xi Jinping of China that the islands would not be militarized, satellite photographs show runways and bunkers for fighter jets. A week ago, an American warship reported that it was forced off course by an extremely close encounter with a Chinese ship seeking to expel it from the area.