WARSAW, Poland (AP) — Poland's president on Tuesday expressed his country's disapproval of a planned Russian-German gas pipeline during a visit by the German president.

Polish President Andrzej Duda said at a joint news conference with Frank-Walter Steinmeier that he believes Nord Stream 2 would undermine the energy security of central and eastern Europe.

The project has become a deeply divisive issue in Europe, with Germany insisting it is purely a business deal.

Running on the Baltic Sea bed, Nord Stream 2 would double the amount of natural gas that Russia can send directly to energy-hungry Germany and other countries in western Europe from newly tapped reserves in Siberia. The pipeline would intentionally skirt eastern European nations like Poland and Ukraine.

Another point of difference between the two presidents was rule of law in Poland, which the European Union says is under threat from the current right-wing government.

Steinmeier told reporters it was an issue he was raising with Duda.

At a later conference on the role of Poland and Germany in Europe, Steinmeier urged Poland to observe EU rules that it adopted when it joined in 2004. He said the EU would be strong and its members sovereign only when they follow the principles they have set for themselves.