But South Korea is unlikely to want to apply any sort of real squeeze on North Korea over the nuclear issue until more negotiation has been tried first.

ECONOMIST: Bucking up the alliance

The leaders are expected to repeat a call from G8 foreign ministers urging North Korea to "fully cooperate" in the verification of its nuclear declaration and settle the issue of the country's past abductions of Japanese nationals.

BBC: G8 summit: The key issues

But China's Assistant Foreign Minister Ma Zhaoxu told the same briefing that the issue of North Korea and its satellite launch wouldn't be on the agenda at the global nuclear-security summit in Seoul next week.

WSJ: China Seeks Peacemaker Role on North Korea

Understand that the concept of the Nuclear Security Summit that we set up was not directed at the specific issue of Iran or North Korea, but was directed at one leg of a multi-legged stool when it comes to our nuclear security.

WHITEHOUSE: President Obama and President Lee Hold a News Conference

Sagan would also like to make it harder for nations to opt out of the Non-Proliferation Treaty, as North Korea has done, such as automatically referring the issue to the UN Security Council and requiring the return of nuclear materials if a withdrawing nation got help from outside.

NPR: Nuclear Weapons Gain Importance for Regional Powers

The U.S. State Department has said North Korea must provide a complete declaration of its nuclear program to the United States and its partners in talks on the nuclear issue -- Russia, China, Japan and South Korea -- to break the deadlock.

CNN: North Korea: U.S. to blame in nuclear talks deadlock

Before talk of a Syrian connection, an article in the March issue of Arms Control Today by Siegfried Hecker and William Liou listed the many ways North Korea's nuclear expertise could be of use to Iran, which also has suspect nuclear ambitions.

ECONOMIST: The devil in the nuclear detail