The United States and North Korea continue to have conversations "virtually every day" in the wake of their leaders' nuclear summit in June, the State Department said Thursday.

U.S. President Donald Trump and North Korean leader Kim Jong-un met in Singapore and agreed to work toward the "complete denuclearization" of the Korean Peninsula in exchange for security guarantees from the U.S.

But skepticism has grown about the implementation of the deal.

"I can tell you, we continue to have conversations, virtually every day, every other day or so," State Department spokeswoman Heather Nauert said at a regular press briefing.

She was asked if the two sides are planning another round of follow-up negotiations.

"When I say conversations, that can be by phone. That can be by message. That can be email," she added. "They take different forms, those conversations do."

U.S. National Security Adviser John Bolton said this week that Trump offered in his latest letter to Kim to send Secretary of State Mike Pompeo to Pyongyang again.

Nauert said she has no travel announcements to make at this time.

Pompeo has made three known trips to Pyongyang. The first two were aimed at laying the groundwork for the summit, while the last trip in July was to flesh out the summit agreement.

Source: Yonhap News Agency