SEOUL (REUTERS) - The top United States envoy for North Korea sought to inject momentum to nuclear talks with Pyongyang, saying he is "absolutely certain" Washington and Seoul can work together to achieve their objective of denuclearisation of the Korean peninsula.

US Special Representative for North Korea Stephen Biegun was in Seoul to meet senior South Korean officials, including his counterpart Lee Do-hoon.

"We have a shared goal here, which is to bring an end to 70 years of war and hostilities on the Korean peninsula," Mr Biegun told Mr Lee at the start of their meeting.

"And the primary requirement for us to get to the end point is to achieve final, fully, verified denuclearisation of North Korea… I am absolutely certain we can do this together."

Over recent weeks, the administration of South Korea's President Moon Jae-in has forged ahead with efforts to engage with the North, stoking US concern over a range of issues, from sanctions enforcement to plans for a no-fly zone between the two Koreas.

Mr Lee said that Washington and Seoul are working to ensure that both countries engage North Korea with a united front.

"Because the denuclearisation process is at a critical juncture, we need to meet up as often as possible to make sure there is no daylight whatsoever between our two allies," Mr Lee said.

While Mr Biegun is not scheduled to visit the North, he said he was eager to begin "working-level negotiations" with the reclusive state as soon as possible.

He said early this month that he had offered to meet his North Korean counterpart, Vice-Foreign Minister Choe Son Hui.

North Korean leader Kim Jong Un vowed to work towards denuclearisation during an unprecedented June summit with US President Donald Trump, but the North's actions have failed to satisfy US demands for irreversible steps to scrap its arsenal, including a full disclosure of nuclear facilities and material.

The US suspended some of its annual military drills with South Korea, but has been wary of providing Pyongyang big economic benefits until it takes further concrete disarmament steps.

US Secretary of State Mike Pompeo, who was in North Korea earlier this month, said he was coordinating with allies for a second summit between Mr Trump and Mr Kim, though there have been few details about any breakthrough since then.