US concerned about Putin's visit to North Korea's impact on Korean Peninsula security, ”closely monitoring”

The U.S. government expressed concern over the deepening of Russian-North Korean relations following Russian President Vladimir Putin's visit to North Korea (18-19), and warned that future support for North Korea from Russia would be "extremely unacceptable."
"We will be watching this very closely," he said. John Kirby, the National Security Council's (NSC) Strategic and Public Affairs Coordinator, said at a press conference on the 17th (local time) that "we have a strong stance on this visit.
"We are not concerned," he said. "What we are concerned about is the deepening of the relationship between the two countries." Regarding the reason for the concern, Kirby said, "The ballistic missiles that North Korea supplied to Russia are still
"Not only could it be used to attack targets in Ukraine, but there could also be some reciprocal measures that could affect security on the Korean Peninsula."
This is because North Korea, which has provided Russia with a large number of artillery shells and ballistic missiles, is concerned about the tangible and intangible costs it may receive from Russia following President Putin's visit to North Korea.
Kirby also said, "At this stage, we have not directly seen all of the categories and outcomes of (Russia-North Korea cooperation)."
"We'll be watching that very, very closely," he said.