WASHINGTON — The Obama administration, detecting what it sees as a shift in decades of Chinese support for North Korea, is pressuring China’s new president, Xi Jinping, to crack down on the regime in Pyongyang or face a heightened US military presence in its region.
In a flurry of exchanges that included a recent phone call from President Obama to Xi, administration officials said they had briefed the Chinese in detail about US plans to upgrade missile defenses and other steps to deter the increasingly belligerent threats made by North Korea’s young leader, Kim Jong Un.
China, which has been deeply suspicious of the US desire to reassert itself in Asia, has not protested publicly or privately as the United States has deployed ships and warplanes to the Korean Peninsula. That silence, US officials say, attests to both Beijing’s mounting frustration with the North and the recognition that its policy of reflexive support for Pyongyang could strain its ties with Washington.
‘‘The timing of this is important,’’ Tom Donilon, Obama’s national security adviser, said in an interview. ‘‘It will be an important early exercise between the United States and China, early in the term of Xi Jinping and early in the second term of President Obama.’’
While administration officials cautioned that Xi has been in office for only a few weeks and that China has a history of frustrating the United States in its dealings with North Korea, Donilon said he believed that China’s position was ‘‘evolving.’’
Judging whether China has genuinely changed course on North Korea is tricky: Beijing has appeared to respond to US pressure before, only to backtrack later. China, the North’s only strong ally, has long feared that the United States would capitalize on the fall of the North Korean leadership by expanding US military influence on the Korean Peninsula.
Nor has China given clues about its intentions in its public statements, voicing grave concern about the rising tensions while being careful not to elevate Kim’s stature.
Behind that taciturn reaction, Chinese analysts said, are internal debates within the Communist Party and the military about how to deal with Kim, and how vigorously to enforce the UN economic sanctions that China signed on to last month.
The White House said it was encouraged by how swiftly China supported the sanctions, which followed a North Korean nuclear test and a missile launch. But how energetically China has enforced them is a matter of debate, with some diplomats and analysts saying it has dragged its feet.
In a meeting with two senior US officials who traveled to Beijing two weeks ago to try to persuade China to enforce new banking restrictions on North Korea, Chinese banking leaders showed little sign of compliance, said Marcus Noland, an expert on North Korea at the Peterson Institute for International Economics in Washington.
Many analysts say the sanctions cannot succeed without China’s cooperation, since it has close trade ties with North Korea and has in the past chosen to keep its government afloat by providing fuel and significant aid. Even if China does cooperate, it is unclear how far North Korea might bend; North Korea ignored China’s entreaties not to conduct the nuclear test in February that set off the latest conflict with the United States and South Korea.
In the coming weeks, the White House will send a stream of senior officials to China to press its case, starting with Secretary of State John Kerry, who will travel to Beijing on April 13, on a tour that will also take him to South Korea and Japan.
In the short run, officials said, the administration wants the Chinese to be rigorous in customs inspections to interdict the flow of banned goods to North Korea.
More broadly, it wants China to use its leverage over Kim to persuade him to cease his provocations and agree to negotiations predicated on giving up his nuclear program.