They say coal-fired power plants contribute to global warming and want German firm Siemens to pull out of the project.
ADVERTISEMENTHundreds of climate change protesters have staged rallies outside Siemens' offices across Germany and the Australian embassy in Berlin.
They want the German engineering firm to pull out of involvement with a coal mine project in Australia, amid concerns over global warming.
Siemens CEO Joe Kaeser told reporters the Munich-based company would decide before Monday what to do about its contract to supply signalling systems for a rail link between the Carmichael coal mine and a port.
The vast mine is owned by Indian company Adani, and the signals contract is worth about €18 million to Siemens.
Australia, which is currently battling massive wildfires following months of drought and above-average temperatures, is one of the world's biggest coal exporters.
Kaeser praised the climate activists from the Fridays for Future movement and said he offered an advisory position with Siemens' energy division to one of its leading figures, Luisa Neubauer.
But Neubauer made it clear that the group won't back down from its demand for Siemens to cancel the Australian mine contract.
The activists want Siemens to quit the mine project because they say emissions from coal-fired power plants contribute to global warming.