People wearing protective face masks walk amid concerns over Covid-19  in front of Pyongyang Station in Pyongyang, North Korea April 27, 2020.
Washington CNN  — 

The Biden administration attempted to contact North Korea in the last month to discuss “possible cooperation on humanitarian issues, including Covid-19 cooperation” but they have not received a response, the US Special Representative for North Korea Policy said Tuesday as he warned the US believes the country is preparing for a nuclear test.

The message “was conveyed almost as soon as they made public their Covid outbreak. So I guess it’s — within the past month or so. Because we want to make clear that we continue to separate humanitarian issues from other developmental concerns. And we would like to offer cooperation in helping them deal with the Covid situation,” US Special Representative for North Korea Policy Sung Kim told reporters.

This outreach came after multiple other Biden administration efforts to reach out to North Korea – both directly and through third parties – that have gone unanswered.

“To date the DPRK has not responded and continues to show no indication it is interested in engaging. Instead we have seen a marked increase in the scope an scale of their ballistic missile tests,” Sung Kim said.

The International Atomic Energy Agency said Tuesday that North Korea is “readying their nuclear test site,” and that the situation surrounding North Korea’s nuclear program “is quite concerning because we have seen a fast-forward in every line.”

“They are building more facilities to enrich uranium. They are operating their reprocessing plant, which is what takes plutonium out of fuel, which is another way to have more material for more bombs,” IAEA Director-General Rafael Grossi told CNN.

Sung Kim also said, as other US officials have, that the US “assess that the DPRK is preparing to conduct a seventh nuclear test.” He added that he did not have any specific information about the exact timing of the possible nuclear test.

Last month US military and intelligence agencies assessed that North Korea could be ready to resume underground nuclear testing at its Punggye-ri site, based on satellite images showing signs of personnel and vehicle activity there.

North Korea also launched eight ballistic missiles from various parts of the country over the weekend which “would be the largest number of ballistic missiles ever launched in a single day by the DPRK,” Sung Kim Kim said.

North Korea has now launched 31 ballistic missiles in 2022, the most ballistic missiles it has ever launched in a single year, surpassing its previous record of 25 in 2019.

South Korea and the US responded on Monday with eight missile launches of their own, the third time time this year they have staged tit-for-tat missile tests.

On Tuesday the two countries put on an aerial show of force to North Korean leader Kim Jong Un, flying 20 fighter jets over waters west of the Korean Peninsula in response to Pyongyang’s recent missile tests.

The allies sent the jets – South Korean F-35A, F-15K and FK-16 fighters and US F-16s – over the Yellow Sea, known as the West Sea in South Korea, on Tuesday morning following North Korea’s launch of eight short-range ballistic missiles on Sunday.

Despite North Korea’s continued provocations Sung Kim said that the Biden administration is prepared to engage diplomatically with the country without preconditions and has encouraged allies and partners to engage diplomatically with North Korea as well. Sung Kim did not put a deadline on when the Biden administration would turn away from seeking diplomacy.

“On the timeline for our commitment to a diplomatic approach, there is no end date for that. I think we will continue to remain committed to pursuing a viable diplomatic path to pursue the complete denuclearization of the Korean peninsula and to address issues of concern to both sides,” Sung Kim said, noting that the Biden administration will also keep sanctions in place.

Brad Lendon and Yoonjung Seo contributed reporting.