The US has urged China to cut back on supplies to North Korea as part of the international effort to make the reclusive Communist regime abandon its nuclear weapons.
If China were to reduce that support, it would be "powerfully persuasive" in Pyongyang, John Bolton, the American Ambassador to the UN, said as US Secretary of State Condoleezza Rice prepared to visit Beijing.
"They've not yet been willing to do it," he said, but "China has a heavy responsibility here." Mr Bolton was speaking just after the UN Security Council unanimously passed a US-sponsored resolution imposing sweeping sanctions to punish the reclusive Communist regime after last Monday's nuclear test.
China - which shares an 880-mile border with North Korea and is conduit for a large part of the latter's imports and exports - will be pivotal if the sanctions are to succeed.
Chinese reservations forced the US to water-down the original terms of the resolution. Immediately after the vote, Beijing signalled it would not join in inspecting North Korea imports and exports for illicit weapons.