Warsaw (Poland) | Once rock-solid, the support that Ukraine has gotten from its biggest backers for its fight against Russia is showing cracks.

Political posturing in places like Poland and Slovakia, where a trade dispute with Ukraine has stirred tensions, and Republican reticence in the United States about Washington's big spending to prop up Ukraine's military have raised new uncertainties about the West's commitment to its efforts to expel Russian invaders more than 18 months into the war.

And Russian President Vladimir Putin, who hopes to outlast allied backing for Kyiv, will be ready to capitalise if he sees Ukraine is running low on air defence or other weapons.

The West has long been shoulder-to-shoulder with Ukraine against Russia. But between Ukraine's impassioned, unending pleas for help, and huge handouts from its backers, signs of discord have emerged.

In July, Britain's defence minister at the time said Ukraine should show “gratitude” to the West, after Kyiv renewed its vocal — but unsuccessful — push to join NATO.

This week, a new bout surfaced after Ukraine filed a complaint at the World Trade Organisation against three neighbours and European Union members — Hungary, Poland and Slovakia — for banning imports of Ukrainian farm products, a key export for the war-weary country's battered economy.

The three bristled at the move, with Polish Prime Minister Mateusz Morawiecki shooting back that his country is “no longer transferring any weapons to Ukraine because we are now arming ourselves with the most modern weapons”.

Some EU officials have warned that Putin is revelling at the new show of Western discord at a time when Ukrainian troops are making slow gains in their counteroffensive against Russian forces, who still control a vast swath of eastern and southern Ukraine.

Still, from Washington to Warsaw, where the military cost and capabilities of helping Ukraine are at issue, officials are playing down any talk of a rift.

”I don't believe that one political dispute will lead to a breakdown,” Polish President Andrzej Duda said, adding that his prime minister was only referring to newly ordered weapons that wouldn't ever go to Ukraine anyway.

Jake Sullivan, the Biden administration's national security adviser, said on Thursday he believed that “Poland will continue to be a supporter of Ukraine”.

Ukrainian President Volodymyr Zelenskyy, in a brief visit to Washington this week, sought to shore up US support for his country, which has factored into the political campaign ahead of next year's presidential election. Former President Donald Trump and leading GOP rival Gov. Ron DeSantis of Florida say they want the US to stop sending weapons to Ukraine.

Sen. Joe Manchin, D-West Virginia, after meeting with Zelenskyy on Thursday, acknowledged that “people are talking about how much money” is being spent. But, he added, “We're investing in democracy.” Other GOP presidential hopefuls like former Vice President Mike Pence, former South Carolina Gov. Nikki Haley and former New Jersey Gov. Chris Christie support Ukraine.

Politics over the issue is also playing out in Eastern Europe. Lithuanian President Gitanas Nauseda, a big backer of Ukraine's fight against Russia, appealed on the X platform, formerly known as Twitter, for his counterparts in Ukraine and Poland “to resolve current differences,” and said his country was ready to “facilitate” dialogue between them.

Piotr Buras, a Warsaw-based senior fellow at the European Council of Foreign Relations, said, “Polish-Ukrainian relations have become hostage to the Polish electoral campaign,” referring to the country's parliamentary elections next month.

Nonetheless, the harm from Morawiecki's comments lingers, he warned.

“It does a great deal of damage to the Ukrainian cause, as this narrative resembles and legitimises those voices in Europe (mainly on the far-right) that question the need to supply weapons to Ukraine,” Buras said in an email.

Robert Fico, a two-time prime minister in Slovakia, has returned as a front-runner in that country's parliamentary elections. His populist, left-wing party has staked out a pro-Russia stance and vowed to reverse Slovakia's military and political support for Ukraine if elected in the September 30 vote.

Niklas Masuhr, a military analyst at the Centre for Security Studies at the Federal Institute of Technology in Zurich, said it's conceivable that some political parties might “put their eggs in a nationalist basket to ... curry favour with the electorate” and avoid the impression of giving ”undue solidarity to Ukraine" at the expense of domestic interests.

“It would be naive to assume that there are no trade-offs between individual NATO countries' interests and Ukrainian interests," said Masuhr, who called Poland a “strident supporter” of Ukraine when it came to delivery of military equipment.

“There is broad strategic overlap, but that doesn't mean that in every case these interests are aligned,” he said. Issues like energy or food supplies are "critical, or if you will, neuralgic, points in the relationship between these countries”.

Daniel Fried, a former US ambassador to Poland and now a senior fellow at the Atlantic Council think tank, said the recent standoff in Eastern Europe was “not the end of the Polish-Ukrainian alliance” and pointed to Duda's effort to walk back the comments by his prime minister.

“This mini-crisis may have peaked,” Fried said by phone from Berlin. "This is going to happen ... in a war kind of situation where people's nerves are fried, and there are real issues at stake.” “I'm reasonably confident this will be patched up and is in the process of being patched up — at least I hope so,” he said.