The United States chief envoy for North Korea sought to give a boost to nuclear talks on Monday, saying he was “absolutely certain” Washington and Seoul could work together to secure the denuclearisation of the Korean Peninsula.

“We have a shared goal here, which is to bring an end to 70 years of war and hostilities on the Korean Peninsula,” Stephen Biegun, told South Korean counterpart Lee Do-hoon as the two met in Seoul.

“The primary requirement for us to get to the end point is to achieve final, fully, verified denuclearisation of North Korea,” he added. “I am absolutely certain we can do this together.”

In recent weeks, South Korea has pushed ahead with efforts to engage with North Korea, raising US concerns over a range of issues from sanctions enforcement to a proposed no-fly zone between the two Koreas.

Lee said Washington and Seoul are working to ensure both countries engage North Korea in 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,” he said.

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

He said early this month 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 summit with US President Donald Trump in June, but North Korea’s actions have failed to satisfy US demands for irreversible steps to scrap its arsenal, including a full disclosure of nuclear facilities and material.