In the dispute over a takeover of Twitter, high-tech billionaire Elon Musk has responded with a counterclaim against the short message service.
Musk filed the lawsuit as "confidential" in the Delaware court in which Twitter is suing the founder of electric carmaker Tesla, the court said on Friday.
The lawsuit cannot therefore be examined.
Shortly before, the responsible judge had set the start of the process on October 17th.
The richest person in the world had the planned takeover of Twitter for a price of 44 billion dollars (around 43 billion euros) burst on July 8 because of allegedly "false and misleading" information from the short message service.
In particular, he accuses Twitter of having too few spam or fake accounts on the platform.
Twitter described this justification as "hypocrisy" and wants to take legal action to force Musk to complete the contractually agreed purchase.
Five days of negotiations are scheduled for the process.
Observers consider a judicial defeat of Musk and thus a forced fulfillment of the takeover agreement to be quite conceivable.
It is also possible that the multi-billionaire would have to pay Twitter a contractual penalty of up to one billion dollars.