(Bloomberg) -- The US is seeking clarification from Poland over its support for Ukraine after Polish officials suggested that the country, a key ally, may halt military aid to the country, according to a senior US defense official. 

The official, who requested anonymity to discuss US policy, said Poland remains committed to backing Ukraine, but the country’s exact stance is unclear. Polish Prime Minister Mateusz Morawiecki said earlier this week that the country has halted weapons supplies to Ukraine, escalating a dispute with its eastern neighbor that’s undermining a vital alliance in Kyiv’s fight against Russia.

Though both sides later called for easing the tensions, the highly public dispute cast sudden doubt on the unity that had defined the neighbors’ relationship. The spat, which began over Ukrainian grain shipments that have become a political liability for Poland, risked compromising European solidarity with Ukraine against Russia’s invasion. 

Still, the US official said that differences among allies have not yet amounted to cracks in the unity of the coalition that has supported Ukraine, an effort that the official said would likely take stretch into multiple years. 

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Polish diplomats have privately reassured foreign counterparts that the country’s military support for Ukraine will continue, even if on a smaller scale, according to a European diplomat. The person said that losing Poland’s support could prove detrimental to Ukraine’s war effort as it risks undermining NATO unity. 

Counteroffensive Plans

The US defense official official added that Ukraine is making steady progress in its counteroffensive against Russia, while conceding that this was taking longer than the US and Ukraine had originally hoped because of extensive Russian defensive positions. The official said that Ukraine is advancing on the ground in a deliberate and steady fashion and is now able to strike behind Russian lines, disrupting its supplies and its command and control systems.

By preserving combat power, Ukraine is keeping the capabilities to advance as far as the Sea of Azov — a key goal that would enable Kyiv to cut off the main Russian forces in Ukraine from their supply base in Crimea — once it manages to pierce through the Russian defenses, the official said.  

Ukrainian President Volodymyr Zelenskiy said late Thursday that the counteroffensive will continue into the autumn and winter in order to deprive Russia of the pause he said it needs to rebuild forces. 

Zelenskiy was in Washington for meetings with President Joe Biden and congressional leaders. Biden informed him that the US has agreed to his request to provide ATACMS long-range missiles to Ukraine, according to people familiar with the discussions.

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