Russia has requested military equipment from China, triggering concerns the move will hamper Western efforts to supply weapons for Ukraine, reports say.
US officials say Moscow had asked Beijing for military aid since the start of the invasion last month, reports the Financial Times.
Other US officials said that Russia is running short of some weapons as the conflict drags into its third week.
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The US is also preparing to warns its allies about the Russian requests to China, reports say.
The Biden administration has refused to comment.
A spokesperson for the Chinese embassy in Washington, said they were unaware of any suggestions that China might be willing to help Russia.
"China is deeply concerned and grieved on the Ukraine situation," the spokesperson said.
"We sincerely hope that the situation will ease and peace will return at an early date."
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The reports emerged as US National Security Adviser Jake Sullivan prepares to meet with his Chinese counterpart, Yang Jiechi, in Rome on Monday.
US officials, including White House press secretary Jen Psaki, have been increasingly critical of Beijing's response to Russia's war in Ukraine.
While Beijing has seemingly tried to strike a neutral tone on the international stage, Chinese domestic media coverage has promoted Russian disinformation campaigns and described the war as a "special military operation."
Psaki also tweeted on Wednesday that Beijing "has seemingly endorsed" false Russian claims that the US is developing chemical weapons in Ukraine.
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Russian President Vladimir Putin met his Chinese counterpart Xi Jinping on the side lines of the Beijing Winter Olympics last month and the two nations issued a joint statement affirming a partnership "without limits".
Sullivan told CNN on Sunday that the US has made it clear to Beijing that there will "absolutely be consequences" for "large-scale" efforts to give the Kremlin a workaround to US sanctions.
"We will not allow that to go forward and allow there to be a lifeline to Russia from these economic sanctions from any country anywhere in the world," he said.
- Reported with CNN
