US Defense Secretary Lloyd Austin told CNN that President Joe Biden has "been very clear about the fact that we won't have troops engaged in combat with Russia in Ukraine," CNN reported.

Austin said that if the US were to put into place a no-fly zone, it would require controlling the skies, engaging Russian aircraft, and taking out aircraft systems in Ukraine, Belarus, and Russia.

"So that would mean that we're in combat with Russia. These are two nuclear powered countries that nobody wants to see engage in the conflict. It's not good for the region. It's not good for the world," he said.

He said the US is focused on providing the type of assistance to Ukraine that "we know are making a difference" and doing "everything within our power to defend every inch of NATO territory."

Austin was also asked about China's position on the war in Ukraine.

Austin told CNN that it's "hard to say" what China will do and declined to speculate.

"I would hope that China would not support this despicable act by Putin, I would hope that they would recognize a need to respect sovereign territory," he told CNN, adding that, "We've been clear that if they do that, we think that's a bad choice."

Russia has also requested military support and economic assistance support from China, two US officials told CNN this week.

China has conveyed some openness to offering help to Russia, according to a US diplomatic cable to allies. Both Russia and Beijing have denied that there have been any such requests

On Friday, President Joe Biden sought to dissuade China's President Xi Jinping from assisting Russia, warning his Chinese counterpart—during a 110-minute long video call—of the "implications and consequences" for Beijing if it were to provide material support to Moscow.