The Biden administration has ruled out setting up a no-fly zone for Russian aircraft over Ukraine, with senior defense officials saying enacting one would put the United States "in the fight" – as President Biden has maintained that U.S. military will not fight in Ukraine.

Ukraine President Volodymyr Zelenskyy said Monday that the West should consider imposing a no-fly zone, without going into detail about how it would be enforced.

"The president has been clear that U.S. troops, U.S. forces, will not be used inside Ukraine," the official said. "That includes in the use of a no-fly zone."

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"There’s the commander in chief who has made it very, very clear, and there’s no discussion about it here, there’s no debating about it here" at the Pentagon, the official said.

Damage is pictured after shelling by Russian troops of central Kharkiv, northeastern Ukraine. (Vyacheslav Madiyevskyy/ Ukrinform/Future Publishing via Getty Images)

A no-fly zone is "just not going to happen," the official added.

Biden, last week, authorized an additional 7,000 U.S. troops to Germany, and said the U.S. "will defend every inch of NATO territory with the full force of American power."

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"Let me say it again — our forces are not and will not be engaged in the conflict with Russia in Ukraine," Biden said. "Our forces are not going to Europe to fight in Ukraine, but to defend our NATO allies and reassure those allies in the East."

"There is no doubt, no doubt, that the United States and every NATO ally will meet our Article IV commitments, which says, an attack on one is an attack on all," Biden said.

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Last month, Defense Secretary Lloyd Austin put 8,500 U.S. troops on heightened preparedness.

President Biden is seen during a 30-minute phone call with Ukraine President Volodymyr Zelenskyy on Tuesday, March 1, 2022, in this photo released by the White House. (White House)

Biden said he spoke with Austin and Chairman of the Joint Chiefs of Staff Gen. Mark Milley about "preparations for additional moves should they become necessary to protect our NATO allies and support the greatest military alliance in the history of the world, NATO." 

Russia's invasion of Ukraine stretched into a sixth day Tuesday. Satellite imagery showed a 40-mile Russian convoy menacing the Ukrainian capital of Kyiv.

A defense official said, though, that the Russian convoy has made "no appreciable movement" toward Kyiv and soldiers are running out of food. 

The official said there is "no reason to doubt" reports that Russian soldiers are also punching holes in their own fuel tanks to stop their vehicles advancing.

A residential building is seen damaged after yesterday's Russian missile attacks in Vasylkiv, Kyiv Oblast, Ukraine on March 1, 2022. (Wolfgang Schwan/Anadolu Agency via Getty Images)

Biden and Zelenskyy spoke Tuesday for just over 30 minutes, a White House official told Fox News.

Zelenskyy said the two leaders discussed "American leadership on anti-Russian sanctions and defense assistance to Ukraine."

The White House said Biden "underscored the United States’ sustained help for Ukraine, including ongoing deliveries of security assistance, economic support, and humanitarian aid."

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Part of the discussion centered around ways Russia will be held accountable for the invasion of Ukraine, including sanctions that the White House said are "already having an impact on the Russian economy."

The two also discussed increased attacks on areas occupied by Ukrainian civilians, including a bombing close to the Babyn Yar Holocaust memorial.

Fox News' Peter Aitken, Jennifer Griffin and The Associated Press contributed to this report.