The United States warned Wednesday against North Korea's potential provision of additional military aid to Russia for use in Ukraine, as Pyongyang's top diplomat visited Moscow this week in an apparent sign of deepening bilateral ties.

At the invitation of Russian Foreign Minister Sergei Lavrov, North Korean Foreign Minister Choe Son-hui visited Russia from Monday to Wednesday, during which she also met with Russian President Vladimir Putin.

"Clearly, North Korea and Russia have a relationship," Maj. Gen. Patrick Ryder told a press briefing. "What we don't want to see is the continued proliferation of aid to Russia to be used in Ukraine."

Asked to comment on the North's recent launch of what it claims was a hypersonic intermediate-range ballistic missile, Ryder called on Pyongyang to refrain from "destabilizing" activity.

"When it comes to destabilizing activity, we will continue to call on North Korea to refrain from such activity and will continue to consult closely with our allies in the region to ensure that we can maintain regional peace and security," he said.

In a separate briefing, State Department spokesperson Matthew Miller urged the North to come back to dialogue.

"We call on the DPRK to refrain from further provocative destabilizing actions and statements and to return to diplomacy," he told a press briefing, referring to the North by its official name, the Democratic People's Republic of Korea.

"In particular, we encourage the DPRK to engage in substantive discussions on identifying ways to manage military risks and create lasting peace on the Korean peninsula," he added, reiterating the US harbors "no hostile intent" toward the North.

On the North Korean foreign minister's trip to Russia, Miller took note of arms transfers between the two sides that the US has criticized as a violation of multiple U.N. Security Council resolutions.

"We've seen Russia providing weapons to North Korea. We've seen North Korea providing weapons to Russia," he said. "We've seen Russia taking actions in violation of multiple U.N. Security Council resolutions, including ones that it itself supported." (Yonhap)