The United States is depending heavily on China to rescue a faltering diplomatic effort to negotiate an end to North Korea's nuclear weapons but has suggested no specific pressure tactics to Beijing, senior US officials said Thursday.

Talks involving China, the United States, Russia, Japan and South Korea have been sidelined for nearly a year while concerns mount within the administration that North Korea may be preparing for a nuclear weapons test.

The officials, speaking on condition of anonymity, said they were unable to verify published reports China has dismissed the idea of sanctions to pressure North Korea to abandon its nuclear weapons program. If China has taken such a decision it has not advised the administration, said a senior US official speaking on condition of anonymity.

The United States has reached out to China because of its strong economic and political ties to the Pyongyang government, while in the meantime publicly offering North Korea one-on-one talks with US negotiators once six-party negotiations are resumed.

In their talks with the Chinese, Secretary of State Condoleezza Rice, Assistant Secretary of State Christopher Hill and other American diplomats have left it up to the Chinese to decide what tactics to use, the senior US official said.