In the five months since Russia launched its war in Ukraine, the United States has pledged about $24 billion in military aid to Ukraine. That’s more than four times Ukraine’s 2021 defense budget. America’s partners in Europe and beyond have pledged an additional $12 billion, according to the Kiel Institute for the World Economy.

And yet these tens of billions still fall short of the Ukrainian government’s wish list for weapons, which President Volodymyr Zelensky’s government announced last month. This divergence between what Ukraine wants and what its Western partners are prepared to give reflects the reality that Western leaders are pulled in two directions. They are committed to helping Ukraine defend itself against Russia’s aggression, but they are also trying to prevent the conflict from escalating into a major power war.

But escalation, though incremental and thus far contained in Ukraine, is already underway. The West is providing more and more powerful weapons, and Russia is unleashing more and more death and destruction. For as long as both Russia and the West are determined to prevail over the other in Ukraine and prepared to devote their deep reserves of weapons to achieve that goal, further escalation seems almost preordained.

The United States and its allies should certainly continue providing Ukraine with the matériel it needs, but they should also — in close consultation with Kyiv — begin opening channels of communication with Russia. An eventual cease-fire should be the goal, even as the path to it remains uncertain.

Starting talks while the fighting rages would be politically risky and would require significant diplomatic efforts, particularly with Ukraine — and success is anything but guaranteed. But talking can reveal the possible space for compromise and identify a way out of the spiral. Otherwise, this war could eventually bring Russia and NATO into direct conflict.

The current U.S. approach assumes that would happen only if the Ukrainians are given particular systems or capabilities that cross a Russian red line. So when President Biden recently announced his decision to provide Ukraine with the multiple-launch rocket system that Kyiv says it desperately needs, he deliberately withheld the longest-range munitions that could strike Russia. The premise of the decision was that Moscow will escalate — i.e., launch an attack against NATO — only if certain types of weapons are provided or if they are used to target Russian territory. The goal is to be careful to stop short of that line while giving the Ukrainians what they need to “defend their territory from Russian advances,” as Mr. Biden said in a statement in June.