Analysts pointed to the still unclear responses from China and South Korea, the impoverished North's two largest benefactors who have kept Kim's government afloat with billions of dollars in trade and aid out of fear that a messy collapse of the Pyongyang government could generate an economic disaster of refugees flooding across their borders. South Korea has been unclear about what impact a test would have on its detente with the North, which has included the construction of tourism resorts and a vast industrial park on the other side of the border. But analysts were mostly watching reaction from China, which has the power to cut off flows of oil into North Korea.
In Beijing, a professor at the influential Central Party School argued that China's approach to its reclusive neighbor had been too soft.
"South Korea, Russia and China share the same idea on this -- no war, no sanction, no violence against North Korea. These countries have given Kim Jong Il a wrong signal, a protective screen, that he can do whatever he wants," said Zhang Liankui, a North Korea expert and professor at the school's Institute for International Strategic Studies. "Peaceful negotiations had been undertaken many times, but what is the result? It is a failure."
U.S. officials had particularly put stock in China's ability to control the North Koreans, faith that analysts now say appears to have been ill placed. The Chinese, publicly and unambiguously, warned the North Korea's against testing since they announced their attention to do so last Tuesday. But the North, long thought to be under China's sphere of influence, seems to have dismissed Beijing's orders.
"The North Koreans are making a statement that 'you guys can gang up on us, but you can't change us,' " said Lho Kyong Soo, international relations professor at Seoul National University. "Now, they're hoping they could get away with this like Pakistan. They're saying treat us with respect and accept us this way because we are not going to change."washinton post
In the long-term there isn't realistically much that the rest of the world can do about this. The international community has very few options.
A military attack from America is out of the question because it would result in a significant war. South Korea wouldn't stand for that and I do not think the American public would either.
I think we will see sanctions. There may be some sort of shipping blockade but that won't have much of an impact as North Korea does not have significant tradetimes
Charter of the United Nation
The Security Council may decide what measures not involving the use of armed force are to be employed to give effect to its decisions, and it may call upon the Members of the United Nations to apply such measures. These may include complete or partial interruption of economic relations and of rail, sea, air, postal, telegraphic, radio, and other means of communication, and the severance of diplomatic relations.
Should the Security Council consider that measures provided for in Article 41 would be inadequate or have proved to be inadequate, it may take such action by air, sea, or land forces as may be necessary to maintain or restore international peace and security. Such action may include demonstrations, blockade, and other operations by air, sea, or land forces of Members of the United Nations.
What will be done is economic sanctions based on article 41, but I am not sure the world is ready for the article 42.
BTW it is interesting to note Richard Lloyd-Parry, Asia Editor of The Times, says
Both politically and culturally, the Japanese are not ready for nuclear weapons in any sense. You can't underestimate the deep aversion to nuclear weapons testing among most postwar Japanestimes