Dec. 18 (UPI) -- To his credit, President Donald Trump is very serious about ending the war in Ukraine. He has pushed diplomacy to its limits.

However, the best of intentions do not always bring success. In Ukraine, two seemingly immovable objects are blocking any peace agreement.

One is Russian President Vladimir Putin. The other is Ukrainian President Volodymyr Zelensky. Putin cannot back down and believes that it is in the best interests of the Trump administration to place Russia at a higher priority than Ukraine for the long term. In terms of realpolitik, Putin is correct.

If Trump can improve relations with Russia, as well as shift the burden of European defense to Europe, would that not be a win-win? The flaw, however, is that no one in Europe trusts Putin. And frankly, without substantial U.S. presence, there would be no NATO. That reason is clear.

No united states of Europe exists today. Nor will one exist in the future. And a pillar of Europe -- the United Kingdom -- is no longer in the European Union. Hence, this combined Putin-Trump vision is a mirage.