(TNND) — The U.S. is cutting back on weapons shipments to Ukraine.

And that could make the path to a ceasefire between Russia and Ukraine more difficult, according to a Russian foreign policy expert.

Mark N. Katz, a professor emeritus of government and politics at George Mason University, said ceasefires happen when both sides feel that they’re in a stalemate.

“Cutting back on U.S. arms shipments would encourage (Russian President Vladimir) Putin to think that he's not in a stalemate, that if he just keeps going, then he can make additional gains,” Katz said. “So, that's what concerns me.”

The Trump administration reportedly plans to hold back some weapons that were planned for delivery to Ukraine after a Defense Department review determined American arsenals were running too low.

The Associated Press cited officials who spoke on condition of anonymity that the U.S. would withhold some air defense missiles, precision-guided artillery and other weapons.

Defense Secretary Pete Hegseth told lawmakers at a defense budget hearing a few weeks back that they’re calling on European allies to do more heavy lifting for security on their continent.

Sen. Chris Coons noted that the 2026 budget request eliminated aid to Ukraine.

Hegseth said they made some “hard choices” in the budget to realign with the administration’s priorities.

“A negotiated peace in Ukraine makes America look strong, makes us look like we understand the state of the world and where we want to be focused, even if we understand that Russia is the aggressor and we applaud the efforts of the Ukrainians,” Hegseth said during the June 11 Senate hearing. “There is a moment where you have to recognize what exists on the battlefield and that a better outcome is a negotiated peace to stop the killing and stop the slaughter, and our budget reflects that perspective.”

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The U.S. has been Ukraine’s largest donor, with about $67 billion in military assistance sent to Ukraine since Russia launched its invasion in February 2022.

“Well, I think the timing is unfortunate, with Russia making bigger than ever attacks with drones and missiles on Ukraine,” Katz said of the new plans to hold back weapons shipments. “Obviously, this is a time when Ukraine needs air defense systems.”

Katz said the U.S. should ramp up weapons shipments at a time when Putin is being more aggressive.

He said this is a desperate phase for Putin, who is making advances that are slow and costly.

Katz said Putin has good reason to push the envelope to increase the pace of the war before the strain catches up with him.

Putin hasn’t shown a real willingness to negotiate a ceasefire.

“He'll only stop this if he's too afraid to continue,” Katz said.

Katz doesn’t doubt the U.S. is running low on some weapons.

“The thing about American weaponry, it's obviously highly effective. But the problem is that because it's so sophisticated and expensive, we don't produce it in bulk,” he said.

Katz said weaponized drones, for example, can be produced cheaper and faster. And that might be a lesson for the U.S. stemming from this conflict, given Ukrainian successes with such weapons.

Katz doesn’t think Putin and Ukrainian President Volodymyr Zelenskyy are close to reaching a ceasefire.

He said Ukraine is willing to cooperate with Trump on a ceasefire, which would likely mean some acceptance of territory already lost.

But a ceasefire that allows Russia to keep what it’s already captured isn’t good enough for Putin, Katz said.

“They want more, apparently a lot more,” Katz said.

Russia already controls over 44,000 square miles of Ukraine, or close to a fifth of the country, including Crimea and parts of Donbas that Russia had seized before its 2022 invasion.

Russia has taken over another 27,000 square miles of Ukraine since its invasion over three years ago.

“Putin, if he wanted to, could paint it as a victory,” Katz said.

But Katz said that Putin wants the Ukrainians to retreat from more territory and accept limits on their armed forces.

He wants the West to end military assistance to Ukraine and formally declare that Ukraine will never become a NATO member, Katz said.

But Katz said Ukrainians would be very fearful that giving in to Putin’s demands would just set them up for invasion later.

“He wants Ukraine to be maximally vulnerable to Russia,” Katz said.