When Kim Yong-nam, North Korea’s ceremonial leader, attended the Iranian presidential inauguration this month, he flew via Moscow, even though a flight via Beijing would have been much more convenient.

To some observers, the choice of stop-over is emblematic of a North Korean regime that seems increasingly estranged from its Chinese ally over irs nuclear ambitions and more reliant on long-standing ties with Russia. Pyongyang’s shift of attention also creates a potential opening that US diplomats are keep to explore as they search for ways to curb North Korea’s fast-developing nuclear missile programme.

“The North Koreans are offended with China, and many of their political contacts are either frozen or seriously narrowed,” said Valery Sukhinin, Russia’s former ambassador to Pyongyang and one of Moscow’s most seasoned Korea hands.