The United States said China must join with the rest of the world in imposing strong sanctions against North Korea over its latest nuclear test, given its "special relationship" with the reclusive regime.
U.S. Deputy Secretary of State Antony Blinken made the call Wednesday in Seoul during a a meeting with South Korean Foreign Minister Yun Byung-se.
Pyongyang angered the international community when it announced it had tested its first-ever hydrogen bomb on January 6, despite being under United Nations sanctions over three previous tests.
China is North Korea's closest diplomatic and economic ally, but ties between the two have become strained over the North's failure to end its nuclear ambitions.
Worried about sanctions fallout
But Beijing is also worried that stronger economic sanctions against North Korea will cause the regime to fall, sending scores of refugees over its shared border.
Yun agreed with Blinken's call for tougher sanctions against Pyongyang, saying, "This is North Korea versus the international community."
Blinken will travel to China later Wednesday for talks with officials over the matter.
U.S. Secretary of State John Kerry will travel to Beijing next week to hold further discussions with his Chinese counterparts.