"As we speak today, we have not seen them cross that line," Blinken said in response to a question at a Senate committee on whether China was providing "lethal aid" to Russia.

Blinken has publicly warned for weeks that China is considering Russian requests for weapons to fight in Ukraine, with some reports indicating limited shipments by Chinese companies to Moscow.

President Xi Jinping this week paid a visit to Moscow in which he pushed a Chinese proposal for a ceasefire in the war -- a call met with skepticism by Washington, which fears Russia would use a pause to regroup battered forces on the ground.

"I think their diplomatic support, their political support, and to some extent material support for Russia certainly goes against our interest in bringing this war to an end," Blinken said of China.

Blinken also said that the United States would encourage other countries to extradite Russian President Vladimir Putin if he visits following an arrest warrant issued by the International Criminal Court.

"I think that anyone who is a party to the court and has obligations should fulfill their obligations," Blinken said.

He was responding to questions from Republican Senator Lindsey Graham who said the United States should arrest Putin if he steps on US soil.

The United States is not part of the court in The Hague, with the previous Republican administration of Donald Trump imposing sanctions on the then ICC prosecutor for probing US military actions in Afghanistan.

Blinken said he did not expect Putin to travel to the United States. Russia is part of the Asia-Pacific Economic Cooperation forum, which holds its summit in November in San Francisco, but it is highly unlikely the United States would invite Putin.