North Korea said Wednesday it successfully tested a new hypersonic missile it implied was being developed as nuclear-capable, as it continues to expand its military capabilities and pressure Washington and Seoul over long-stalled negotiations over its nuclear weapons.

The missile test early Tuesday was North Korea’s third round of launches this month and took place shortly before North Korea’s U.N. envoy accused the United States of hostility and demanded the Biden administration permanently end joint military exercises with South Korea and the deployment of strategic assets in the region.

A photo published in North Korea’s state media showed a missile mounted with a finned, cone-shaped payload soaring into the air amid bright orange flames. The official Korean Central News Agency said the missile during its first flight test met key technical requirements, including launch stability and the maneuverability and flight characteristics of the “detached hypersonic gliding warhead.”

The North’s announcement came a day after the South Korean and Japanese militaries said they detected North Korea firing a missile into its eastern sea. The U.S. Indo-Pacific Command said the launch highlighted “the destabilizing impact of (North Korea’s) illicit weapons program.”

North Korea last week made offers to improve relations with the South if certain conditions are met, apparently returning to its pattern of mixing weapons demonstrations with peace overtures to wrest outside concessions.

Negotiations over its nuclear program have been in a stalemate since February 2019. North Korea has demanded the lifting of U.S.-led sanctions while insisting it has the right to a nuclear weapons program. U.S. officials have made it clear the sanctions will stay in place until the North takes concrete steps toward denuclearization.

North Korean leader Kim Jong Un in recent political speeches has vowed to bolster his nuclear deterrent in the face of U.S. pressure. His government has so far rejected the Biden administration’s offer to resume talks without preconditions, saying that Washington must abandon its “hostile policy” first, a term North Korea mainly uses to refer to sanctions and joint U.S.-South Korea military drills the North considers to be an invasion rehearsal.

At a ruling party meeting in January, Kim named hypersonic glide vehicles, which are launched from a rocket before gliding into a target, among a wish-list of sophisticated military assets. KCNA described the new missile as an important addition to the country’s “strategic” weaponry, implying that the system is being developed to deliver nuclear weapons.