North Korea has no plans to abandon its nuclear development programme, a top official from Pyongyang has told China, official media said on Wednesday.

A day after North Korea's foreign minister told The Associated Press that his country is ready to halt its nuclear tests if the United States suspends its annual military exercises with South Korea, President Barack Obama said Sunday that Washington isn't taking the proposal seriously and Pyongyang would "have to do better than that."

A senior U.S. diplomat stepped up pressure on China on Wednesday to play a leading role in punishing North Korea for its recent nuclear test that raised worries about advancements in its bomb program.

An unusually blunt Secretary of State John Kerry said Thursday that China's diplomatic strategy to defuse the North Korean nuclear strategy simply hasn't worked.

North Korea's main ally China says it "firmly opposes" Pyongyang's purported hydrogen bomb test and is monitoring the environment on its border with the North near the test site.