The United States is "confident" that China is considering providing lethal equipment to support the Russian forces invading Ukraine, according to CIA director William Burns.

Such a step by China would be "a very risky and unwise bet," the intelligence chief said in an interview aired Sunday on CBS's "Face the Nation."

"I hope very much that they don't."

His comments, along with others Sunday by national security adviser Jake Sullivan, constituted the latest blunt US warning to China against providing lethal weaponry.

But both Burns and Sullivan made clear that the United States has yet to detect signs that any arms have been shipped.

"We actually haven't seen them take a final decision... and we haven't seen the aid be provided to Russia," Sullivan said on CNN's "State of the Union."

US officials quoted by the Wall Street Journal say China is considering sending drones and munitions to Russia. China has denied such a move.

With the conflict entering its second year, Burns suggested that Russian President Vladimir Putin is nowhere near close to engaging in serious peace talks.

He repeatedly used the word "hubris" to describe the Russian leader's state of mind.

"I think Putin is, right now, entirely too confident of his ability... to wear down Ukraine, to grind away," he said.

Putin "believes today that he cannot win for a while, but he can't afford to lose," said Burns, a former deputy secretary of state.

But at some point, he added, the Russian leader is "going to have to face up to the increasing costs as well, in coffins coming home" and in "cumulative economic damage."

Burns described a conversation he had in Ankara in November with Russian spy chief Sergei Naryshkin. Rather than detecting any readiness to negotiate, he said their talk was "pretty dispiriting."

But Burns said he had conveyed to Naryshkin "the seriousness" of US warnings against Russia ever resorting to nuclear weapons in Ukraine. And he added it was "very valuable" that the leaders of China and India had separately underscored that point.

As the war drags on, US officials have stepped up their warnings to Beijing that delivering lethal weaponry to Moscow could have profound consequences.

President Joe Biden said Friday that he does not "anticipate a major initiative" from China to provide weapons to Russia.

But his comments came days after Secretary of State Antony Blinken said China was "considering providing lethal support."

Biden said he had told Chinese President Xi Jinping last summer that a move to arm Russia would have dire economic repercussions.

"Without any government prodding, 600 American corporations left Russia, from McDonald's to Exxon," he said he told Xi.