North Korea’s National Defense Commission, the country’s most powerful body, on Thursday threatened a “higher level” test of a nuclear warhead “targeted at the U.S.” The impending test is no surprise, since satellite photos showed preparations almost a year ago.

More striking is the vitriol directed at the United Nations Security Council, which on Tuesday approved new sanctions on the North as punishment for its December 12 missile test. Pyongyang accused the other members of the Council of “backstage dealings with the U.S.” and “blind hand-raising.” That can only be read as a swipe against China, the Kim family’s main international patron.

The hostility suggests some tension in the relationship, but then we’ve been here before. The Chinese media have been reporting for weeks that the North had informed Beijing of its intention to conduct a nuclear test and was resisting attempts to convince it to stop. China’s vote for new sanctions is less important than its follow-through in implementing existing measures. Until Beijing restricts trade flows for more than a few weeks at a time, one should be cautious in declaring a split.