Let me just briefly review the elements of our strategy against proliferation. It helps our nonproliferation strategy when we can remind Russia or China of their legally-binding obligations under the NPT, the CWC, or the BWC not to assist other countries acquire those weapons. Again, it doesn't solve all the problems in a single stroke, but it gives us another tool to stroke with. Sanctions have a key role. Nobody likes them much, but the conventional wisdom that they never work is wrong.
Sanctions also warn others that proliferation entails costs.
Of course a sanction becomes a positive inducement when you remove it. Activating the 1985 peaceful nuclear cooperation agreement with China was done in the context of significant Chinese actions to phase-out even peaceful nuclear contacts with Iran. Of course our most controversial positive inducements are light water-reactors and interim heavy fuel oil deliveries, linked to North Korea's commitments under the Agreed Framework. Technical support . Assuming a commitment to control sensitive technologies and goods, some countries, particularly of the former Eastern bloc, don't know how.