"China will strongly oppose (a test or launch) and will be sure to implement future United Nations resolutions even more resolutely," said Zhang Liangui, a North Korea expert with the ruling Communist Party's main research and training institute in Beijing.
China may also take unilateral steps such as cutting back on cross-border trade, Chinese experts say. Such measures could target the industrial commodities and luxury goods Kim needs to keep the moribund North Korean economy ticking over and ensure the loyalty of regime supporters.
Iran might be North Korea's only reliable friend.
UPDATE: I'm sure the pucker factor of seeing so many North Korean subs put to sea at once back in August has something to do with this:
South Korea is seeking to buy about twenty retired American S-3 anti-submarine warfare (ASW) aircraft to augment South Korean ability to find and destroy North Korean submarines.
Yeah, that would be a good idea.