BEIJING (AP) -- Chinese officials have told the U.S. that they've tightened inspections and policing along the border with North Korea as part of U.N. sanctions aimed at halting Pyongyang's nuclear and missile activities, the top U.S. diplomat for East Asia said Friday.
Beijing's action reflects a growing awareness about the urgent need for China to pressure North Korea into halting its testing of missiles and nuclear bombs, Acting Assistant Secretary of State Susan Thornton told reporters in Beijing. President Donald Trump's administration has made a renewed push to enlist Beijing's help in those efforts following a meeting between Trump and Chinese President Xi Jinping last month.
Touching on other areas of the relationship, Thornton said the new administration has not changed its commitment to greater engagement with countries in the Asia-Pacific region or its approach to naval operations in the disputed South China Sea.
On North Korea, the U.S. has seen a "shift in emphasis" in China's approach to its fellow communist neighbor, Thornton said.
"They've said that they have stepped up border inspections, beefed up sort of the policing function on the border, stepped up customs inspections," she said. Beijing has also done "a number of other things on companies" that have dealings with North Korea, Thornton said, without giving details.
The U.S. has been talking to Beijing about taking action against specific firms and is waiting to see what sort of action China will take, she said.
China has signed on to U.N. sanctions and suspended coal imports from North Korea through the rest of the year, but has been generally reticent about what other steps it may be taking to use its leverage as Pyongyang's most important trading and diplomatic partner.
Asked about Thornton's remarks, Chinese foreign ministry spokesman Lu Kang said China remained committed to "strictly implementing" U.N. sanctions but offered no details or what other measures it might be taking.
Lu also reiterated China's call for a renewal of six-nation denuclearization talks that have been on ice since 2009, saying the parties should "be flexible, meet each other halfway, and return to the negotiating table as soon as possible."
Thornton said the U.S., China and others were also in talks on a future U.N. resolution on North Korea in order to cut the time needed to take action following another nuclear or missile test.
"So we're looking at trying to get going on the next set of major measures that would be taken in the wake of another provocation," Thornton said. Such measures could include ratcheting up economic pressure on the North by targeting trade in consumer goods, possibly including textiles, she said.
Despite Lu's comments later in the day, Thornton said Beijing officials now realize more pressure is needed before dialogue can be restored.
"And so they know now that they don't have, I think, as much time to try to bring the North Koreans to the table, get their calculus changed and get them to the negotiating table as they may have previously thought," she said.
Adding to that, Beijing also seems to have recognized that North Korea's actions were "undermining China's own security in pretty major ways," Thornton said.
"They do recognize that it's going to be pretty hard to have a dialogue while the North Koreans are shooting off missiles," she said.
North Korea exploded two nuclear devices last year, one of which it claimed was a hydrogen bomb. Satellite imagery suggests it could be ready to conduct its next test --- its sixth --- at any time.
On Monday, Pyongyang said it is ready to start mass-producing a new medium-range missile after a weekend test-launch confirmed its combat readiness. The regime's oft-stated goal is to perfect a nuclear warhead that it can put on a missile capable of hitting Washington or other U.S. cities.
Some outside the administration have been less sanguine about China's willingness to work with the U.S. on North Korea, while Beijing officials say their influence with Pyongyang has been exaggerated. China maintains that while it wants to neutralize North Korea as a threat, it opposes harsh sanctions or other measures that could bring down young leader Kim Jong Un's regime, leading to a potential outflow of refugees and South Korean and American troops on the Chinese border.
China continues to pay lip service to cracking down on North Korea but there's been "little evidence of actual pressure," said Dean Cheng of the Heritage Foundation think tank in Washington.
Cheng also criticized China for pressuring South Korea not to deploy a sophisticated U.S. anti-missile system aimed at countering North Korea. Beijing says the system threatens its own security with its ability to peer deep into northeastern China.
"In short, China has made clear that Seoul, even in the face of North Korean missile tests, should place Chinese concerns above the security of their own people," Cheng said.
While there have been reports that the Trump administration was reconsidering Barack Obama's "pivot" to Asia, Thornton said Washington has made no substantial changes.
That followed the U.S. Navy's sailing a destroyer near a Chinese man-made island in the South China Sea on Thursday in a "freedom of navigation" operation aimed at challenging what the U.S. considers excessive territorial claims in the strategic waterway that Beijing claims virtually in its entirety.
Washington's approach is "engagement with Asia to show that we're still present in the region, that we're going to keep our security commitments in the region, certainly support for our allies and with North Korea as a focal point on the security front," Thornton said.