President Lee’s Summit with China Fails to Create Agreement on North Korea Engagement
It now appears the Chinese are not too eager to assist South Korea on the North Korea issue:

South Korea’s presidential office said the two leaders reaffirmed that peace and stability on the Korean Peninsula — an apparent reference to the denuclearization of North Korea — are shared interests, and confirmed China’s willingness to play a constructive role.
China’s Ministry of Foreign Affairs made no reference to peace and stability on the Korean Peninsula in its readout of the summit.
Doo Jin-ho, a senior analyst at the Korea Institute for Defense Analyses, said China’s unresponsiveness on the North Korean issue fell short of South Korea’s expectations.
“Beijing did not appear to roll up its sleeves to the extent Seoul may have hoped, nor did it take a particularly forward-leaning stance on the North Korean nuclear issue,” Doo said.
You can read more at the link, but I did not expect the Chinese to do much of anything on this issue. Right now the North Koreans are having all their needs met by the Russians, which means the Chinese do not have as much influence as they have had in the past over the Kim regime. China also probably looks at pressuring North Korea as a waste of time because they understand that North Korea will engage with South Korea when they want to, not because the ROK demands they do.

