WASHINGTON -- The United States and South Korea are working closely together on their joint response to North Korea, the State Department said Thursday following Seoul's announcement of high-level inter-Korean talks next week.

The Seoul government said the two sides will meet at the border village of Panmunjom Monday to discuss the implementation of April's summit agreement and preparations for a follow-up meeting between South Korean President Moon Jae-in and North Korean leader Kim Jong-un.

"We are in close contact with the Republic of Korea about our unified response to North Korea," a spokesperson for the State Department said in response to a Yonhap query.

In the April agreement, Kim committed to the complete denuclearization of the Korean Peninsula. He reaffirmed the pledge in a historic meeting with US President Donald Trump in Singapore in June.

The two Koreas have launched various joint projects, including on railways and forestry, as part of their summit agreement to promote cross-border reconciliation.

The spokesperson recalled Moon's commitment to rid the North of its nuclear weapons program.

"As President Moon stated, 'the improvement of relations between North and South Korea cannot advance separately from resolving North Korea's nuclear program," he said.

Progress on denuclearizing North Korea has reportedly been slow despite Trump's assertion that the nuclear threat is over following his meeting with Kim.

North Korean officials have complained that the US insists on keeping international sanctions on the regime until its denuclearization while Pyongyang has halted nuclear and ballistic missile testing and dismantled several related sites.

Pyongyang has also demanded that Washington quickly declare a formal end to the 1950-53 Korean War to create the conditions necessary for peace on the peninsula.

The three-year conflict, in which the US fought alongside South Korea, ended in an armistice, not a peace treaty, leaving the sides technically at war. (Yonhap)