Poland’s nationalist government is looking into whether it can demand reparations from Germany for damages inflicted in World War II – in a move likely to heighten growing tensions between the neighboring countries.

Arkadiusz Mularczyk, a parliamentarian from the ruling Law and Justice party, said Wednesday that he has commissioned a report, due next week, into whether Poland can legally proceed with a claim.

The issue has resurfaced amid a surge of patriotic sentiment this week as Poland observes the anniversary of the failed 1944 Warsaw Uprising against Nazi rule, which resulted in the destruction of the capital and the deaths of as many as 200,000 civilians. Amid this national focus on the war – in which nearly 6 million Poles were killed – senior politicians have called on Germany to make amends, with Defense Minister Antoni Macierewicz saying Tuesday that Germany had to “pay back the terrible debt they owe to the Polish people.”

Berlin has given the idea short shrift, pointing to a 1953 agreement under which Poland’s former Communist government waived its right to compensation. Ulrike Demmer, deputy spokeswoman for the German government, insisted the issue was closed, and added that Germany had already made “significant reparations for general war damage, including to Poland, and is still paying significant compensation for Nazi wrongdoing.”

But with Macierewicz and other senior politicians countering that the 1953 agreement could not be considered binding as it was made by a “Soviet puppet state,” Poland doesn’t look set to drop the issue any time soon. Law and Justice leader Jaroslaw Kaczynski, who also called for reparations during his stint as prime minister a decade ago, told a conservative Polish radio station this week that his government was “preparing itself for a historical counteroffensive.”

“We are talking here about huge sums, and also about the fact that Germany for many years refused to take responsibility for World War II,” he said.

Tensions have grown between Germany and Poland, important trading partners and neighbors, since Law and Justice came to power in 2015 and began pushing ahead with a conservative, nationalist agenda that has increasingly driven a wedge between Warsaw and its European Union partners to the west. Poland views Germany, Europe’s economic powerhouse, as having an undue influence over the bloc.