WARSAW, Poland (AP) —

Poland is set to release a long-announced report Thursday on the cost to the country of years of Nazi German occupation as it marks 83 years since the start of World War II.

Poland’s right-wing government argues that the country which was the war’s first victim has not been fully compensated by neighboring Germany, which is now one of its major partners within the European Union.

Top leaders including ruling party head Jaroslaw Kaczynski, who is Poland's chief policy maker, and Prime Minister Mateusz Morawiecki are to attend the ceremonial release of the report at the Royal Castle in Warsaw. It is to be the main point of national observances of the anniversary of the war that began Sep. 1, 1939, with Nazi Germany's bombing and invading Poland, for more than five years of brutal occupation.

A team of some 30 economists, historians and other experts have worked on the report since 2017. The issue has created bilateral tensions.

Poland's government rejects a 1953 declaration by the country's then-communist leaders, under pressure from the Soviet Union, agreeing not to make any further claims on Germany.

Germany argues compensation was paid to East Bloc nations in the years after the war and calls the matter closed.

An opposition lawmaker, Grzegorz Schetyna, says the report is just a “game in the internal politics” and insists Poland needs to build good relations with Berlin.

Some 6 million of Poland’s citizens were killed in the war and its industry, infrastructure and culture suffered huge losses.