Nearly one year after Russia invaded Ukraine, new questions are rising over China’s potential willingness to offer military aid to Moscow in the increasingly drawn-out conflict.

In an interview that aired Sunday, U.S. Secretary of State Antony Blinken said American intelligence suggests China is considering providing arms and ammunition to Russia, an involvement in the Kremlin’s war effort that he said would be a “serious problem.”

China has refused to criticize Russia for its actions or even to call it an invasion in deference to Moscow. At the same time, it insists that the sovereignty and territorial integrity of all nations must be upheld. The question now is whether China is willing to convert that rhetorical backing into material support.

Here's a look at where China stands on the conflict.

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DOES CHINA BACK RUSSIA IN ITS WAR ON UKRAINE?

China has tried to walk a fine — and often contradictory — line on the Russian invasion.

China says Russia was provoked into taking action by NATO's westward expansion. Just weeks before the Feb. 24, 2022, invasion, Chinese President Xi Jinping hosted Russian President Vladimir Putin in Beijing for the opening of the Winter Olympics, at which time the sides issued a joint statement pledging their commitment to a “no limits" friendship. China has since ignored Western criticism and reaffirmed that pledge.

Also Read: Russia to test new hypersonic missile in drills with China and South Africa

But China has yet to confirm the visit Putin has said he expects from Xi this spring.

China is “trying to have it both ways," Blinken said Sunday on NBC. "Publicly, they present themselves as a country striving for peace in Ukraine, but privately, as I said, we’ve seen already over these past months the provision of non-lethal assistance that does go directly to aiding and abetting Russia’s war effort.”

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HAS CHINA PROVIDED MATERIAL SUPPORT TO RUSSIA?

So far, China's support for Russia has been rhetorical and political, with Beijing helping prevent efforts to condemn Moscow at the United Nations.

Blinken, at a security conference in Munich, Germany, said the United States has long been concerned that China would provide weapons to Russia and that “we have information that gives us concern that they are considering providing lethal support to Russia in the war against Ukraine.” That came a day after Blinken held talks with Wang Yi, the Chinese Communist Party’s most senior foreign policy official, in a meeting that offered little sign of a reduction in tensions or progress on the Ukraine issue.

“It was important for me to share very clearly with Wang Yi that this would be a serious problem,” Blinken said, referring to potential military support for Russia.

The U.S. ambassador to the United Nations, Linda Thomas-Greenfield, also expressed her concern about any effort by the Chinese to arm Russia, saying “that would be a red line.”

Also Read: Putin, Xi vow closer ties as Russia bombards Ukraine again

Russian and Chinese forces have held joint military drills since Russia invaded Ukraine a year ago, most recently sending ships to take part in exercises with the South African navy in a key shipping lane off the South African coast.

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WHAT HAS CHINA SAID ON THE MATTER?

Following the meeting between Wang and Blinken, China's Foreign Ministry issued a statement that it has always played a constructive role in the Ukraine conflict by adhering to principles, encouraging peace and promoting talks.

The ministry said the China-Russia partnership “is established on the basis of non-alignment, non-confrontation, and non-targeting of third parties,” and that the U.S. was adding “fuel to the fire to take advantage of the opportunity to make profits.”

Beijing says it has continued a normal trade relationship with Russia, including purchases of oil and gas, as have other countries such as India. However, that trade is seen as throwing an economic lifeline to Moscow, but there have been no documented cases of China providing direct aid to the Russian military along the lines of the inexpensive military drones that Iran sells to Moscow.

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WHAT COULD HAPPEN IF CHINA AIDS RUSSIA?

“To the best of our knowledge, they haven’t crossed that line yet,” Blinken told NBC on Sunday.

Blinken did not specify what measures the U.S. could take in response to Chinese military support for Russia, but efforts to put a floor under ties that have deteriorated to their lowest level in decades have so far been unsuccessful. The U.S. has sought to limit Chinese access to the latest microprocessors and manufacturing equipment, and has continued to challenge Chinese territorial claims in the South China Sea.

For China, the most sensitive issue is U.S. support for Taiwan, the self-governing island democracy that Beijing considers its own territory to be conquered by military force if deemed necessary. Taiwan is a major customer for U.S. defensive arms and has hosted a growing number of prominent American elected officials, enraging Beijing.

Meanwhile, U.S. Congress members have called for the banning of TikTok and other Chinese-owned social media platforms, as well as increased sanctions on Chinese firms backed by the Communist Party, which wields ultimate control over the Chinese economy and suppresses independent media and political opposition voices.