Ukrainian President Volodymyr Zelenskyy this week said that if the U.S. cannot guarantee a quick path toward NATO membership, then there are alternative security options Kyiv would accept: nuclear weapons. 

But don't think the United States is eager to agree to those terms. 

"The chance of them getting their nuclear weapons back is somewhere between slim and none," retired Lt. General Keith Kellogg, special envoy to Ukraine and Russia, told Fox News Digital. "Let's be honest about it, we both know that's not going to happen."

In 1994, following the collapse of the Soviet Union, Ukraine agreed to give Russia its nuclear arms in exchange for reassurances from Russia, the U.S. and the U.K. that its sovereignty and independence would be respected – a treaty Moscow has violated with its repeated invasions – and in an interview on Tuesday, Zelenskyy argued that Ukraine should be given its arms "back" if a timely NATO membership is off the table.

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But Kellogg, the man tasked by President Donald Trump to help bring an end to the three-year war, said rearming Ukraine with nuclear weapons is a non-starter.

"Remember, the president said we're a government of common sense," he said. "When somebody says something like that, look at the outcome or the potential. That's using your common sense."

Zelenskyy on Tuesday confirmed his willingness to meet with Russian President Vladimir Putin face-to-face if that is the best option for bringing an end to the war, though the Kremlin chief has not agreed to any in-person meeting with the Ukrainian leader.

Trump on Sunday said that initial talks had begun with both Ukraine and Russia, and Kellogg this week confirmed that Kyiv and Moscow will need to make concessions if there is going to be a peace deal.

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The administration has been tight-lipped on what sort of compromises will need to be made, particularly when it comes to the biggest hot-button issue for both Zelenskyy and Putin: Ukrainian NATO membership. 

Kellogg wouldn’t comment on where Trump lands when it comes to backing either Ukraine with a membership in the security alliance or Russia in denying its southern neighbor access to the top coalition.

"That’s one of the reasons I’m going next week to Europe, to actually see them face-to-face," he said. "I can bring that back to the president and say, ‘OK, Mr. President, this is their concern. This is what the issues are.’"

Kellogg is set to travel to the Munich Security Conference, which runs Feb. 14-16, where he said he will meet with world leaders to discuss Russia’s war in Ukraine and get a better idea of where nations like the U.K., Germany and Denmark, along with other top providers of military aid to Ukraine, stand on negotiations to end the war.

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"As you develop the plans to end this carnage, you have to make sure that you've got the feel of everybody in play," Kellogg said. "Once we get to have these face-to-face discussions, then you can really kind of work … on concessions."

NATO Secretary General Mark Rutte last month urged member nations to increase their support for Ukraine, an issue he said is vastly important when it comes to bolstering NATO deterrence in the face of the Russia, China, North Korea, Iran bloc.

"If we get a bad deal, it would only mean that we will see the president of Russia high-fiving with the leaders of North Korea, Iran and China, and we cannot accept that," Rutte said. "That will be geopolitically a big, a big mistake."

Rutte has urged NATO nations to ramp up defense spending and warned that if Russia comes out on top in this war, it will cost NATO allies "trillions" not "billions."

Kellogg will also press NATO allies to increase defense spending and, as directed by Trump, to start shouldering the burden of the war in Ukraine.