White House National Security Council spokesman John Kirby told reporters Wednesday the United States has concerns about any kind of potential defense cooperation between Russia and North Korea.
Kirby said the U.S. is carefully monitoring the contacts between Moscow and Pyongyang.
"No nation on the planet, nobody should be helping Mr. Putin kill innocent Ukrainians. And if they decide to move forward with some sort of arms deals, well, obviously we'll take a measure of that, and we'll deal with it appropriately," he said.
Russian President Vladimir Putin met Wednesday with North Korean leader Kim Jong Un at Russia's most advanced spaceport amid warnings from the U.S. and South Korea against a potential arms transfer.
Kim pledged his "full and unconditional support" for "all decisions" by Putin, in an apparent reference to Russia's war on Ukraine, during talks at the Vostochny Cosmodrome in the Amur region of Russia's Far East, near the Chinese border.
Kim also invited Putin to visit North Korea and Putin accepted, North Korean state media reported.
"Kim Jong Un courteously invited Putin to visit the DPRK at a convenient time," according to KCNA, referring to North Korea by its official name.
Earlier, media reports quoted unidentified Western officials as saying Russia hopes to receive North Korean artillery shells for use in the war in Ukraine, while Pyongyang appears to want advanced technology for its satellites and nuclear-powered submarines, as well as food assistance from Moscow.
"We need to discuss the issues of economic cooperation and humanitarian issues, as well as the situation in the region," Putin told Kim.
The two first toured the spaceport, where reporters asked if Russia would help North Korea build satellites.
"That's why we came here," Putin said, according to Russian state media. "The leader of the DPRK shows great interest in rocket engineering; they are also trying to develop space."
DPRK refers to North Korea's official name, the Democratic People's Republic of Korea.
As Kim visited Russia Wednesday, North Korea fired two short-range ballistic missiles into the sea off its eastern coast. South Korea's military said the missiles were launched from near Pyongyang and flew about 650 kilometers.
Ahead of the talks, South Korean officials said they were closely monitoring the first meeting between Kim and Putin in four years.
"Cooperation between Russia and North Korea should be made in the direction of contributing to peace and prosperity on the Korean peninsula while adhering to the relevant U.N. Security Council resolutions," a spokesperson from South Korea's foreign ministry said on Wednesday.
The U.S. and South Korea have renewed warnings to North Korea not to provide munitions to Russia that could be used in the war in Ukraine.
"Any transfer of arms from North Korea to Russia would violate multiple United Nations Security Council resolutions," said U.S. State Department spokesperson Matthew Miller during a Tuesday briefing. "We will monitor what happens and will not hesitate to take action to hold those accountable if necessary."
Analysts have taken note of China's silence on the Putin-Kim talks. They said China is cautiously managing the situation and reluctant to be drawn into the controversy as the world eyes the arms deal talks between North Korea and Russia.
"China does not have to broadcast its position" on the summit and thereby highlight tensions over Ukraine as it prepares to host the Asian Games in Hangzhou, according to Jung Dae-jin, the director of the Han Peace Institute at Halla University in South Korea.
Others, including Professor Lee Byong-Chol from Kyungnam University's Institute for Far Eastern Studies, question whether Russia is willing to provide North Korea with advanced technology.
Lee told VOA Wednesday that Russia will transfer technology to North Korea, as requested by Kim, but Moscow will only transfer very basic technology.
Russian media reported that Kim and Putin had no plans to sign official documents after concluding their one-on-one meeting. Kremlin spokesman Dmitry Peskov said on Wednesday the talks were "important and substantive."
Kim held his first summit with Putin on April 25, 2019, in the Russian port city of Vladivostok.
Cindy Saine and Lee Juhyun contributed to this report. Some information came from Associated Press and Reuters.