The US has recently begun seeing "disturbing" trendlines in China's support for Russia's military and there are signs that Beijing wants to "creep up to the line" of providing lethal military aid to Russia without getting caught, US officials familiar with the intelligence told CNN.
The officials would not describe in detail what intelligence the US has seen suggesting a recent shift in China's posture, but said US officials have been concerned enough that they have shared the intelligence with allies and partners at the Munich Security Conference over the last several days.
Secretary of State Antony Blinken raised the issue when he met with his Chinese counterpart, Wang Yi, on Saturday on the sidelines of the conference, officials said.
Vice President Kamala Harris also alluded to China's support for Russia during a speech in Munich.
"We are also troubled that Beijing has deepened its relationship with Moscow since the war began," Harris said Saturday. "Looking ahead, any steps by China to provide lethal support to Russia would only reward aggression, continue the killing, and further undermine a rules-based order."
Officials said the US is seeing China publicly trying to present itself as a proponent of peace --Wang Yi said at Munich on Saturday that Beijing would be introducing a "peace plan" for Ukraine and Russia -- and maintain relationships with Europe, while at the same time quietly aiding Russia's war effort and considering the provision of lethal aid.
On Saturday at the conference, Wang Yi said, "This warfare cannot continue to rage on. We need to think about what efforts we can make to bring this warfare to an end."
As CNN has reported, the Biden administration last month raised concerns with China about evidence it has suggesting that Chinese companies have sold non-lethal equipment to Russia for use in Ukraine, in an effort to ascertain how much Beijing knows about the transactions, according to two US officials.
That equipment has included items like flak jackets and helmets, multiple sources familiar with US and European intelligence told CNN. But China has stopped short of the more robust military assistance, like lethal weapons systems for use on the battlefield in Ukraine, that Russia has requested because it has not wanted to be seen as a pariah on the world stage, officials said.
But there are signs now that Beijing could now be considering it, the officials said, and Biden administration officials are warning publicly and privately that the US is monitoring closely for any violations of western sanctions prohibiting military support for Russia.
China and Russia publicly declared a "friendship without limits" just before Russia invaded Ukraine last year, and Wang Yi is set to visit Russia this month, CNN has reported.