BERLIN (AP) — Thousands are marching in Berlin to demand that Germany make a quick exit from using coal-fired energy, a day before a U.N. climate summit opens in neighboring Poland.

Saturday's march through Berlin's government district and a simultaneous event in the western city of Cologne were organized by environmental groups. Many demonstrators carried flags with slogans like "Stop Coal!" and "The future is coal-free."

The summit opening Sunday in the Polish city of Katowice seeks to build on the landmark 2015 Paris accord, when countries agreed to try to limit global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) by the century's end.

German officials had hoped to present a blueprint for phasing out Germany's use of coal over the coming decades. But an expert committee postponed its report on that until after the U.N. conference.