"I spoke with Foreign Minister Kang about the Inter-Korean talks held on Monday," he wrote. "The US and the ROK remain in close cooperation to ensure the final, fully verified denuclearization of the DPRK. We believe progress can be made."

ROK refers to South Korea's formal name, the Republic of Korea, while DPRK refers to the North's official name, the Democratic People's Republic of Korea.

In their phone call Tuesday (Seoul time), Kang briefed Pompeo on the results of Monday's inter-Korean talks, during which the sides agreed to arrange a third meeting between South Korean President Moon Jae-in and North Korean leader Kim Jong-un in Pyongyang next month.

The new summit, according to some experts, could help break an apparent impasse in negotiations between Washington and Pyongyang to implement their leaders' agreement reached in June.

At the historic summit in Singapore, Kim committed to the "complete denuclearization" of the Korean Peninsula in exchange for US President Donald Trump's commitment to provide security guarantees to the regime.

On reports that Pompeo will soon make his fourth trip to Pyongyang, State Department spokeswoman Heather Nauert said she had no travel announcements.

Speaking at a regular press briefing, she also refused to confirm reports that US and North Korean officials held working-level talks at the inter-Korean border village of Panmunjom over the weekend.

"But negotiations and conversations between our government and North Korea will become sort of a regular course -- part of our regular course of business, where these will be normal," she said, adding that the two sides exchange phone calls and emails. "We will have conversations. We will have meetings. We will have correspondence with the North Korean government as we look to denuclearize North Korea."

A readout from the State Department of the phone call said Kang and Pompeo discussed "DPRK denuclearization efforts and the need to maintain pressure until we achieve the final, fully verified denuclearization of the DPRK as agreed by Chairman Kim."

North Korea has halted nuclear and ballistic missile testing and appeared to take steps to dismantle a missile engine testing site in line with Kim's agreement with Trump.

But experts say such actions are not irreversible and impossible to verify without outside inspection.

Pompeo has urged the international community to strictly enforce United Nations Security Council resolutions against Pyongyang until the regime fully denuclearizes.

The resolutions, which were adopted in the wake of North Korea's nuclear and ballistic missile tests, ban imports of North Korean mineral resources and other goods that are key sources of revenue for the regime.

In their phone call, Kang and Pompeo also "vowed to maintain close coordination and communication and they affirmed the enduring strength of the US-ROK Alliance," according to the readout. (Yonhap)