The clang of hammers and the whine of drills echo through a factory in central Ukraine, as workers assemble hulking armored personnel carriers that troops will soon ride into combat — a cacophony that captures this moment in the war with Russia.

Ukraine has been ramping up domestic arms production significantly, unable to rely as heavily as it once did on an increasingly uncertain supply of weapons from its allies. Last year, Ukrainian Armor, a private company that runs the armored vehicle factory, produced double the number of vehicles it did the year before, according to Vladislav Belbas, the chief executive.

“But that’s not enough,” Mr. Belbas said during a recent visit to the factory, which also includes an assembly line for mortars. “We need to produce more.”

His view reflects a growing sense of reckoning in Ukraine after three and a half years of war. President Trump’s inconsistent support for Ukraine has called into question the continued backing of the United States, Kyiv’s biggest arms supplier. The Trump administration recently paused some arms transfers but then reversed course, agreeing to sell weapons to European allies, which will then give them to Ukraine.

But even with greater certainty about the flow of Western weapons, it still does not match what Ukraine needs to fend off the Russian invasion.