Though there are U.S. official statements, there is insufficient evidence to corroborate. Also, both Russia and China have dismissed allegations.
However, the claim is unverifiable because the U.S. official declined to say what kind of equipment Moscow had requested, and there is no concrete evidence to support this statement.
According to Reuters, a spokesperson for the Chinese embassy in Washington, Liu Pengyu, said he was unaware of Russia's request. He said the current situation in Ukraine is concerning, adding that Beijing desired a peaceful resolution. Further, he said, "The high priority now is to prevent the tense situation from escalating or even getting out of control."
At a regular press briefing on March 14, Chinese Foreign Ministry spokesman Zhao Lijian said that the U.S. had recently published misleading information about China on the Ukraine issue. He also emphasizes that "China's position on Ukraine is clear and consistent, and it has always played a positive role in persuading peace and promoting talks."
According to AP news, in a daily conference call with reporters on March 14, 2022, Kremlin spokesman Dmitry Peskov has denied media reports alleging that Russia sought China's military assistance to advance its offensive in Ukraine. Further, he added, "No, Russia has its own potential to continue the operation, which, as we have said, is unfolding following the plan and will be completed on time and in full."
A report from Politico added that the extent of military support that Russia needs from China is less clear. It quoted Michael Kofman, the Russia director at Virginia-based think tank CNA: "Perhaps Moscow is asking for exploratory talks," and "could be [silicon] chips, which is what they really need. But the majority of semiconductors" he noted, "come from Taiwan, whose government is enforcing the global export restrictions on Russia."
We conclude the claim to be unverifiable at present because U.S. officials have not disclosed complete data on Russia's request, and there is a lack of information.