After his dramatic summit meeting with North Korean leader Kim Jong Un in June, Trump declared on Twitter, "There is no longer a Nuclear Threat from North Korea."

Administration officials were quick to say the actual elimination of that threat would be the subject of negotiations now underway.

And, they said, the trade embargo that China has played a pivotal role in enforcing would ease only after North Korea had taken significant steps to stop developing nuclear weapons and long-range missiles.

The visits by North Korean trade officials in Dandong, along with a boomlet in Chinese tourists to Pyongyang and elsewhere in North Korea, are far from the only signs that Beijing is not waiting.

Instead, it has quietly begun loosening the screws on its long-time ally.

U.S. satellite images and Japanese naval photos have captured suspected illicit ship-to-ship transfers of oil. And experts say North Korean workers are returning to jobs inside China, some under the guise of educational exchanges. Thousands of North Korean laborers also have entered Russia since the U.N. ban against new work permits last September, the Wall Street Journal has reported.

Those workers send home hard-cash wages that, combined with large slush funds likely from prior years of coal sales and clandestine trading networks built up across China and southeast Asia, allow Pyongyang to pursue its nuclear ambitions while keeping its political elite happy with fine liquor, designer watches and the latest electronics normally unobtainable at home.

Some of these transactions, like procuring luxury goods, are clear violations of United Nations resolutions aimed at choking back Pyongyang's nuclear programs.