According to a report in the Hannoversche Allgemeine Zeitung on Monday, the automobile club ADAC is considering leaving its partnership with Deutsche Post.
Insiders told the paper that the idea of the exit was being floated to its shareholders. There have also been talks with Deutsche Bahn to buy out the partnership.
ADAC and Deutsche Post have yet to comment on the rumours.
"We are happy with the cooperation of ADAC," a Post spokesman said.
ADAC Postbus entered the market last year shortly after the long-distance bus competition opened up to all companies.
However, the number of providers of bus journeys across Germany has grown rapidly, causing a price war.
In June, it announced it was expanding with 30 more routes.
To win clients, the ADAC Postbus currently offers fares of €12 for a journey from Berlin to Hamburg. Frankfurt to Cologne will cost passengers €9 and a trip from Berlin to Munich, only €23.
Last month, city2city, once the leader in bus travel, announced it would be turning off the engines in mid-October.
There are around 40 bus operators around Germany. MeinFernbus has about 45 percent of the market share. Flixibus, the second most popular operator, claims 23 percent. Postbus only has eight percent of the market.
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