It was the first time Berlin has formally responded to the class-action suit launched by the Herero and Nama people last year over the tens of thousands killed in the 1904-1908 massacres.
Berlin's position “is that the complaint is inadmissable because of the principle of state immunity”, foreign ministry spokeswoman Maria Adebahr told reporters, a day after a New York judge held a hearing in the case.
“In accordance with US law it was necessary to formally convey this to the court. We did this through a lawyer,” Adebahr said.
The case was postponed, she added, without giving a new date.
Germany has acknowledged that atrocities occurred at the hands of German colonial authorities, but it has repeatedly refused to pay direct reparations.
It has argued that its development aid worth hundreds of millions of euros since Namibia's independence from South Africa in 1990 was “for the benefit of all Namibians”.
Aside from financial compensation, the plaintiffs also want to be included in ongoing negotiations between Germany and Namibia aimed at reaching a joint declaration on the massacres.
The dispute harkens back to a period over a century ago when South West Africa, now known as Namibia, was a German colony.
The suit alleges that from 1885 to 1903 about a quarter of Ovaherero and Nama lands — thousands of square miles — was taken without compensation by German settlers with the explicit consent of German colonial authorities.
It also claims that those authorities turned a blind eye to rapes by colonists of Ovaherero and Nama women and girls, and the use of forced labour.
Tensions boiled over in early 1904 when the Ovaherero rose up, followed by the Nama, in an insurrection crushed by German imperial troops.
In the Battle of Waterberg in August 1904, around 80,000 Herero fled including women and children.
German troops went after them across what is now known as the Kalahari Desert. Only 15,000 Herero survived.
The smaller Nama tribe faced a similar fate. Around 10,000 of them were killed as they sought to rebel against the Germans during the conflict.