WASHINGTON — China’s increasingly icy posture is thrusting Russia forward as North Korea’s preferred diplomatic partner, forcing the Trump administration to turn to Moscow for help in isolating the rogue, nuclear-armed nation.

Beijing’s close ties to Pyongyang have been strained since leader Kim Jong Un ordered the 2013 execution of his uncle who had been the countries’ chief liaison. Since then, the allies once said to be as “close as lips and teeth” have moved further apart over China’s adoption of U.N. sanctions designed to starve North Korea of revenue for its nuclear and missile programs.

But China isn’t North Korea’s only traditionally friendly neighbor. And for the United States, Russia’s increased importance comes at an uncomfortable time. The State Department on Friday warned countries and companies around the world they risk being blacklisted if they do business with dozens of Russian firms. Investigations also continue into allegations Russia interfered in last year’s U.S. presidential election.

“Russia could play a useful diplomatic role,” Joseph Yun, the U.S. envoy to North Korea, said in an Associated Press interview. “If Russia delivers a unified message with the U.S., China, South Korea and Japan that the U.S. is not interested in regime change but rather we want to resolve the WMD issue, they can help better than anyone else to convince them of that.”

Like China, Russia has urged a peaceful resolution as Kim and President Donald Trump trade personal insults and threats of war.