German Chancellor Angela Merkel and her cabinet are due in Warsaw on Friday to hold the 15th iteration of governmental consultations with Poland.

Bilateral cooperation and European and security policy are on the agenda for the talks with Polish Prime Minister Mateusz Morawiecki and his national-conservative Law and Justice Party (PiS).

The last meeting at this level took place in Berlin in 2016.

Relations between Germany and Poland have been strained since the PiS took power in 2015. Warsaw has been critical of German policies on migration and energy, and tensions remain over the payment of reparations for the German occupation of Poland during World War II, as demanded by elements in the PiS.

Ahead of the visit, officials in Berlin said the Polish government had yet to come up with concrete proposals on the issue. Germany stood by its historical responsibility, they said.

Tensions have also been stoked by judicial reforms in Poland that lowered the retirement age of Supreme Court judges and forced the departure of more than 23 judges. The judges were called back as an interim measure after the European Commission referred Poland to the EU's top court, arguing that the country's new law on the retirement age breached fundamental EU values.

Poland's PiS said it was purging the court of corrupt judges, but opponents accused the party of trying to remove critical voices. The PiS has argued that the organization of the judiciary is a national matter.

The European Court of Justice must still rule on whether the Polish reform is in breach of EU rules, a process that could take weeks or months.