Secretary of State Antony Blinken says China pondering supplying weapons to Russia. Live Ukraine updates.

The U.S. has detected worrisome signs of more substantial participation in Russia's war in Ukraine from an influential force: China.

Secretary of State Antony Blinken said from the Munich Security Conference that the Chinese – who a year ago declared their friendship with Russia has "no limits'' – are pondering expanding their backing of Moscow, which so far has not included weapons.

"The concern that we have now is based on information we have that they're considering providing lethal support,'' Blinken told CBS's "Face the Nation'' in an interview that aired Sunday, "and we've made very clear to them that that would cause a serious problem for us and in our relationship.''

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Boosting the Kremlin's diminishing arsenal could not only stack the odds against Western-backed Ukraine but raise the specter of escalating the conflict into a world war. Russia is already getting assistance from Iran, which has supplied it explosive drones mostly used to damage Ukraine's civilian infrastructure.