A monthslong border blockade by Polish truckers is starting to have an effect on Ukrainian soldiers in frozen trenches defending against unrelenting Russian assaults, making already fierce battles even more difficult.

One Ukrainian soldier, Oleksandr, fighting in eastern Ukraine, said that his unit was still waiting for delivery of two night vision devices, critical for soldiers navigating their way to fighting positions safely. The equipment has been held up at the border, he said, where Polish truckers have blocked major crossings, causing miles-long backups, since Nov. 6.

Oleksandr, who asked to be identified by only his first name in accordance with Ukrainian military protocol, was scathing about the action. “To block the borders of the country, during a full-scale invasion, they have to be completely detached from reality, and this way they also wash their hands in the blood of people who are waiting for the necessary help,” he said.

On the surface, the dispute that led to the blockade is simple: Polish truckers are upset about cut-rate competition from Ukrainian drivers who are not subject to the same rules on working hours and wages as drivers from the European Union. The Poles also say they are treated unfairly by Ukrainian customs officials who make them wait while Ukrainian drivers get preference.

The Polish truckers have demanded that the European Union reinstate a permit system for Ukrainian truckers that was lifted after the full-scale Russian invasion of Ukraine, a move that Brussels has been reluctant to make as the war rages on.

Edward Lucas, a senior fellow at the Center for European Policy Analysis, wrote on Sunday that petty wrangles over rules had spiraled out of control. “With strong political leadership, all this would be fixable,” he said.

He added, “The economic pain being felt by Polish and other truck drivers requires targeted assistance: just the sort of problem where the European Union could be useful.”

But as the blockade drags into a second month, the inability of Brussels to address the issue has been compounded by the internal politics of Ukraine and of its neighbors; aggressive Russian propaganda; divergent business interests; and, increasingly, bitter emotions.

Rather than nearing a resolution, the blockade is expanding, with Polish farmers now blocking a fourth major crossing and Slovakian haulers, aided by Hungarian truckers, joining the protest to obstruct another main crossing.

As of Dec. 6, there were an estimated 2,950 trucks stranded on both sides of the Polish border, 650 at the border with Slovakia and 750 waiting to enter Ukraine from Hungary, according to Ukrainian officials.

Ukraine and Poland agreed to open a checkpoint on Monday for a handful of trucks leaving Ukraine. But Poland, along with trucking associations from several other countries, is still calling on the European Union to restore the permit system.

Adina Valean, the European commissioner for transport, told Radio Liberty on Tuesday that she was determined to defend the liberalization of freight traffic between Ukraine and the European Union despite the demands of Polish protesters, making it clear the permit system would not be restored.

The ambassadors of Lithuania, Latvia, and Estonia jointly met with Polish authorities this week to pressure them to find a solution that will end the blockade.

Vasyl Zvarych, Ukraine’s ambassador to Poland, said on Monday that negotiations were continuing and that he was hopeful a compromise could be reached, but, he added, “as long as the Russian aggression is ongoing, we cannot return to these permits.”

“We need to unblock the border and sit down to negotiate, as there is no other way,” Mr. Zvarych said in a statement.

The blockade is expected to lead to a 1 percent drop in Ukraine’s projected economic growth in 2023, according to Yulia Klymenko, head of the Ukrainian Parliament’s transport and infrastructure committee.

“Businesses are not receiving enough components; supply chains are disrupted. This also applies to military equipment and its production,” Ms. Klymenko said last week. “To even assemble drones in Ukraine, you need to bring them in from somewhere else.”

Volodymyr Shul, a Ukrainian soldier who coordinates aid from volunteers for the 63rd Mechanized Brigade, said he did not understand how countries with a vested interest in Ukraine’s victory — and who have been among its most generous allies — could engage in such a blockade at one of the most difficult moments in the war.

Ukraine, he said, is protecting Europe from Moscow’s aggression. “To let Russia advance farther would mean the collapse of Europe and European values,” he added.

Pawel Ozygala, 44, the owner of a transport company in Lublin, Poland, who is taking part in the protests, said it was a matter of basic fairness.

“There is no compromise from Ukrainians, and we don’t want to compromise,” Mr. Ozygala said.

Volodymyr, a driver from the Volyn region of northwestern Ukraine who asked that only his first name be used given the heated emotions around the issue, has been waiting to cross the border for 14 days.

Even though he is caught in the maelstrom, he said, he sympathizes with the Polish truckers and understands why they feel the market conditions are unfair.

“I have very many friends who died at war,” he said. “When the war started, who was the first to open its borders and welcome our refugees? Who was helping us all the time?” he asked. “Poland.”

Finding a compromise has been complicated because Poland is in the midst of forming a new coalition government after a contentious election.

Polish far-right groups, including those with historical links to Russia, have been quick to try to exploit the situation, experts say.

“Russia is profiting from the protests, it’s crystal clear,” said Wojciech Przybylski, director of Res Publica, a Warsaw-based research institution.

The frustration of the Polish truckers is understandable, he said, and as the war grinds on, it is natural that business interests will reassert themselves.

Warsaw, he said, has to step up and offer the truckers assistance, though that is complicated by the messy power transition.

Russia has long been skilled at manipulating divisions in Western societies and at exploiting those fissures for its benefit and has used the trucking issue to paint Ukrainians as ungrateful and untrustworthy, experts say.

Two other neighbors of Ukraine, Hungary and Slovakia, both have leaders openly friendly to Russia and have taken steps that undermine European solidarity for Kyiv. The decision by Hungarian and Slovakian truckers to join the protests threatens to deepen strains on Ukraine’s already battered economy.

Airports in Ukraine have been closed to commercial traffic since the Russian invasion, some of its largest ports remain occupied by Russian forces and the restoration of a shipping lane in the Black Sea allows Kyiv to export only a tiny fraction of what it was able to before the war.

Against that background, roads and rail links are Ukraine’s lifelines.

Although medical, military, and certain food supplies are supposed to be exempt from the truckers’ blockade, Ukrainian soldiers, volunteers and business owners say the chaos is starting to wreak havoc on already precarious supply lines.

Oleksandr, the soldier, said that the fight at the front remained bloody and difficult and that the border blockade added to the feeling that Ukraine was being abandoned.

“I think this action directly plays into the hands of Russia, which is waging war with us and doing everything to destroy our country and people,” he said.