The U.S. State Department expressed alarm over China and Russia's growing alliance.
On Thursday, Chinese President Xi Jinping met with his Russian counterpart Vladimir Putin in Uzbekistan, raising concerns.
It was their first face-to-face meeting since the onset of the Ukraine war, with Xi addressing Putin as "my old friend" and Putin as "dear friend."
In a press conference on Thursday, U.S. State Department spokesperson Ned Price stated that the connection between China and Russia has grown through time rather than "days, weeks, or months."
"Of course, we've seen this relationship move even more closely together. We have made very clear our concern about this deepening relationship and the concern that every country around the world should have about this relationship," he said.
Putin said on Thursday that Xi had concerns and questions about the state of affairs in Ukraine, but applauded the Chinese president for taking a "balanced" stance.
Price noted that while the alliance between Russia and China was "not surprising," Putin's acknowledgment of Xi's worries over the Ukraine war was "striking."
When it comes to the war, Price claimed that Russia is "looking for every conceivable lifeline" and is turning to nations like North Korea and Iran.
Price continued, "China will have to go to extraordinary lengths to even attempt to explain" how the conflict in Ukraine would not "automatically" violate its sovereignty principle.
The United States imposed new sanctions on a long list of Russian officials and companies on Thursday, increasing pressure on Russia over its invasion of Ukraine.
The U.S. sanctions blacklist includes top executives directing Russian securities market activities, a neo-Nazi fighter group, Russian and pro-Russian officials in occupied portions of Ukraine, and a children's rights official who reportedly oversees the deportation of Ukrainian children to Russia.
The GRU spy service and Maxim Oreshkin, President Vladimir Putin's senior economic counselor, have been sanctioned.
According to U.S. intelligence, Russia was seeking security support from China.
"We also made very public the fact that we would be watching very closely and that (China) would incur significant costs if it provided military assistance to Russia in its war or if it aided Russia in a systematic way evade the sanctions that the international community had imposed on it.
"We have not seen (China) do either of those things," Price said.