The Vice President of the European Commission was in Warsaw on Monday ahead of a likely European Union hearing about whether to sanction Poland over its controversial judicial reforms. Critics -- which include France and Germany -- claim the reforms are authoritarian.
Mr Timmermans is trying to persuade Poland's Prime Minister Mateusz Morawiecki to scale these reforms back and show a greater commitment to the "rule of law", which is enshrined as a core EU tenet.
The European Commission last year triggered the so-called Article 7 process that could lead to Poland being punished for breaching EU values. That may result in Poland losing voting rights within EU institutions.
The dispute concerns Poland's controversial overhaul of its supreme court. A third of its judges will be forcibly retired next month.
The Polish government says this a necessary efficiency reform in a judicial system that has not been modernized since the Communist era.
Poland has the support of Hungary, Croatia and the Czech Republic. But Germany, France and other older EU member states back punitive measures to protect the rule of law in Poland and send a message to other EU members considering reforms of their own.
A hearing is likely to take place soon in which EU member states will vote on whether or not to sanction Poland, and if so, what those sanctions will entail.