CHANG: For more than a decade North Korea and Iran have essentially had a joint venture on nuclear weapons and long-range ballistic missiles, and the Chinese have been in the background aiding North Korea in proliferation. This is the nuclear chain reaction.

GERTZ: The Chinese have been the main suppliers of missile technology, and now we have North Korea, a rogue state, which has threatened to fire nuclear missiles at the United States with Chinese made ICBM mobile launchers.

CHANG: The United States has been hesitant to confront China over proliferation. We don't want to anger Beijing leaders. But when some American city is a radioactive slab, it's not going be good enough for an American leader to say: "I could have done something about this, but I didn't want to anger the Chinese."

FISHER: When North Korea and Iran begin selling nuclear missiles to other hostile regimes, then the United States is going to be facing a virtual global whack-a-mole challenge, endless wars, endless challenges, with nuclear armed states.

CHANG: We should be demanding that China stop support of North Korea's nuclear weapons proliferation. China permits Iranian technicians and scientists to transit through its airport, on the way to Pyongyang and back. Every single test of a North Korean nuclear weapon has had Iranian technicians onsite in North Korea. You know, we talk about these Geneva negotiations with Iran, hoping to put the Iranian program in freeze. And we think that if we come to a deal with Iran that we'll be able to do so. The problem is that while we're talking to the Iranians, we have Iranian technicians and scientists in North Korea working on nukes. Take a look at a map, how do the Iranians get to North Korea? Well, we know that they've been transmitting through the Beijing airport. We know this. We track these guys. And what do we do? We do nothing about it. So we're not freezing the Iranian program at all, it's going full speed in the hills of North Korea.