The Biden administration's persistent failure to provide Ukraine with the military supplies it requires poses a serious danger of gifting victory to Russian President Vladimir Putin.
From Abrams tanks to F-16 fighters, US President Joe Biden has constantly dithered over providing Ukraine with the equipment upgrades its forces desperately need if they are to succeed in defending themselves against Russian aggression.
The failure, moreover, to ensure that Ukraine achieves victory in its battle against Moscow's unprovoked invasion has been a key factor in the failure of Ukraine's long-awaited counter-offensive to achieve a decisive breakthrough of Russia's heavily-fortified defences in Ukraine.
Even though it is a year since President Volodymyr Zelensky first made his request to the US and other Western allies to be equipped with superior heavy armour and warplanes, the equipment is only starting to become available on the battlefield now, just as the bitter Ukrainian winter takes hold, thereby severely diminishing its effectiveness.
It was only last month that the first of the 31 US Abrams tanks pledged by the Biden administration were seen in action at an undisclosed location on the Ukrainian battlefield, while the US-made F-16 warplanes, whose delivery to Ukraine was only approved by the White House as late as August, are not due to arrive until next year, with the majority of the warplanes not scheduled for delivery until 2025.
Having raised hopes that this year's Ukrainian counter-offensive would lead to a major breakthrough, Zelensky and his senior commanders are understandably frustrated that progress has been slow, a fact they blame on the inadequacies of the supplies they have received from the US and its allies.
As Zelensky himself conceded in a recent PBS interview, "We didn't get all the weapons we wanted, I can't be satisfied, but I also can't complain too much."
Trying to persuade the Biden administration and the US Congress to maintain their support for Ukraine will top the agenda when Zelensky arrives in Washington this week for crucial talks.
Biden and Zelensky "will discuss Ukraine's urgent needs" as it fights off a Russian invasion, and "the vital importance of the United States' continued support at this critical moment," White House Press Secretary Karine Jean-Pierre said in a statement.
The modest successes achieved by the Ukrainian counter-offensive has certainly not passed unnoticed in Moscow, where Putin believes the tide of the conflict is now turning in his favour.
"I have no doubt that we will certainly achieve all the goals we have set for ourselves," a confident Putin told Russian soldiers this month at an event where he also announced his candidacy for the 2024 elections.
The turnaround in Russia's fortunes in Ukraine is quite remarkable given that only a few months ago the Russian military appeared on the point of collapse after suffering a number of humiliating setbacks. The botched coup attempt in June launched by Yevgeny Prigozhin, the Wagner Group chief who had played a key role in Putin's so-called "special military operation" in Ukraine, undoubtedly marked the nadir of the Russian campaign, raising serious doubts about the Putin's ability to survive in office.
Since Prigozhin's death in a mysterious plane crash in August, however, the Kremlin's fortunes have gradually improved after Putin ordered a dramatic increase in the production of military hardware to make up for the devastating losses in both men and equipment on the battlefield.
By September it was estimated that Russia had in some cases achieved a tenfold increase in the output of missiles, drones, combat vehicles and artillery, which have made a significant contribution to helping the Russians to seize the initiative while the Ukrainians, by contrast, remain desperately short of key ammunition.
The result is that, as this year's fighting season draws to a close with the arrival of winter, Russia finds itself in the surprise position of moving onto the offensive, with Russian forces desperately battling for control of the crucial town of Avdiivka in the Donetsk, widely regarded as the gateway to the Russian-occupied area of Donetsk.
The prospect of Russian forces starting to regain the advantage in Ukraine is certainly a development that the West should view with deep alarm: any form of Russian success in Ukraine would not only spell disaster for Kyiv, but for the wider Western alliance.
Putin has made no secret of his desire to extend Russian military aggression beyond Ukraine to include other regions of eastern Europe, with the head of Polish security recently warning that Nato has just three years to prepare for a Russia attack on its eastern flank.
In such circumstances, therefore, it is vital that the Biden administration not only renews its support for Zelensky during his visit to Washington this week, but also ensures Ukrainian forces receive the equipment they desperately need to defeat Russia.
Only by making certain that Putin suffers a humiliating defeat in Ukraine will the West succeed in deterring autocratic regimes such as Russia, China and Iran from committing further acts of aggression.
Con Coughlin is the Telegraph's Defence and Foreign Affairs Editor and a Distinguished Senior Fellow at Gatestone Institute.
Michelle Barkwell