(Bloomberg) -- Poland’s premier said the country has halted weapons supplies to Ukraine, escalating a dispute with its eastern neighbor that’s undermining a key alliance in Kyiv’s fight against Russia.

“We are no longer transferring weapons to Ukraine, because we are now arming Poland with more modern weapons,” Prime Minister Mateusz Morawiecki said in an interview with Polsat television, in response to a question from a reporter on whether Warsaw would continue to support Kyiv despite a swelling spat over Poland’s ban on grain imports.

He said his government has no intention to “risk the security of Ukraine” and won’t interfere with arms shipments from other countries through the military hub that’s become established in the eastern Polish city of Rzeszow. He noted that Poland is also benefiting financially from the transit.

The remarks, on top of comments by President Andzej Duda aimed at Ukraine’s Volodymyr Zelenskiy in the last 48 hours, mark a dramatic change of tone from Polish leadership. In the months following the start of Russia’s invasion, the government in Warsaw lambasted other Western countries, especially Germany, for being slow in delivering arms to Ukraine. It became one of the biggest donors and the first nation to deliver high-end Leopard tanks in February as well as Soviet era-made gear and ammunition.

The dispute cast sudden doubt on the unity that had defined the neighbors’ relationship before the grain dispute, a friendship that seemed to epitomize European solidarity with Ukraine against the Russian invasion. 

There was no immediate response from Kyiv to Morawiecki’s comments.

“I am not sure that it will have a significant impact” on the war effort, said Peter Schroeder, a former Russia analyst at the US Central Intelligence Agency and now an adjunct senior fellow at the Center for a New American Security.

Poland’s “most important role has been as a transshipment point to get weapons from across NATO and other countries into Ukraine,” he said. “The PM noted that would continue.”

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Morawiecki’s announcement came just hours after Poland turned up the volume in the dispute, summoning Ukraine’s ambassador and threatening to expand a grain ban to other imports from its neighbor.

The government in Warsaw reacted to Zelenskiy’s remarks at the United Nations General Assembly on Tuesday in which the Ukrainian leader accused some European Union countries of feigning solidarity with his war-torn nation and appeasing Russia. 

While Zelenskiy didn’t single out Poland, his language triggered an angry response there. The ruling Law & Justice party is seething over earlier criticism from Kyiv about its decision to unilaterally extend the grain-import ban — a move seen as a pre-election appeal to rural Polish voters.

Duda laid into the Ukrainian leader on Tuesday in New York, comparing Ukraine’s reaction to the grain ban to that of a drowning man, who “can be extremely dangerous, because he can drag you to the depths” and “drown the rescuers.”

The back-and-forth signaled that what seemed to be a relatively minor disagreement has ballooned into something larger. A further worsening could have direct implications for the war, as Poland is the primary destination for refugees and the gateway to about 90% of all the western aid and military equipment headed for Kyiv.

The timing is also a blow to Ukraine, as the war of words flared just as Zelenskiy pressed his case in New York for more global support and Ukrainian forces advance in a grinding counteroffensive to retake occupied territory.

“Tension and disagreements between Kyiv and some of its strongest backers is sure to instill more confidence in the Kremlin that European support for Ukraine is not certain over the long term,” said Schroeder, the former CIA analyst. 

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For Poland, the issue is a political one. The ruling Law & Justice party, seeking a third term in office in next month’s contest, is reluctant to alienate its rural base ahead of a tightly contested election on Oct. 15. 

--With assistance from Daryna Krasnolutska, Peter Martin and Michael Winfrey.

(Updates with details on arms supplies in fourth paragraph.)

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