North Korea is demanding the conclusion of a peace treaty with the United States and a halt to US military exercises with South Korea to end its nuclear tests.
But US Deputy Secretary of State Antony Blinken said on Saturday (local time) Pyongyang needed to demonstrate by its action that it was serious about denuclearisation for any dialogues to start.
"We now have unfortunately a decade during which North Korea has totally reversed its obligations to international community, when it comes to missile and nuclear programs," Blinken told a news conference in Tokyo.
"So it's very hard to take any of their overtures very seriously, particularly in the wake of their fourth nuclear test," he said, after meeting his counterpart from Japan and South Korea.
North Korea said on January 6 it had tested a hydrogen bomb, provoking condemnation from its neighbours and the United States.
The isolated state has long sought a peace treaty with the United States, as well as an end to the exercises by South Korea and the United States, which has about 28,500 troops based in South Korea.
"Still valid are all proposals for preserving peace and stability on the peninsula and in Northeast Asia including the ones for ceasing our nuclear test and the conclusion of a peace treaty in return for US halt to joint military exercises," North Korea's official KCNA news agency cited a spokesman for the country's foreign ministry as saying early on Saturday.
But asked if the United States would consider a halt to joint exercises, US State Department spokesman John Kirby said it had alliance commitments to South Korea.
"We are going to continue to make sure the alliance is ready in all respects to act in defence of the South Korean people and the security of the peninsula," he told a regular news briefing.
Vice foreign ministers from the United States, Japan and South Korea also agreed to seek tough US sanctions on Pyongyang, calling for China to take more actions.
China is North Korea's main economic and diplomatic backer, although relations between the Cold War allies have cooled in recent years.