The Swiss bank is reportedly suing the Japanese conglomerate for millions over a troubled Greensill obligor.

Zurich-based Credit Suisse launched discovery proceedings against Softbank in U.S. court, the «Financial Times» (behind paywall) reported on Friday. It is a part of a bid to recoup $440 million from Katerra, a now-defunct construction firm that was backed by the Japanese investor and was also a Greensill client.

Credit Suisse reportedly halted new business with Softbank as well as with founder-CEO Masayoshi Son – reportedly a client of its wealth arm – seven months ago. Softbank was a backer of Greensill, which is at the center of a $10.1 billion fund blow-up at the Swiss bank.

Credit Suisse In Dark?

Specifically, Katerra drew $440 million from Greensill, a now-insolvent U.K. supply chain financier. The debt was sold to Credit Suisse's funds, as low-risk investments. The Swiss bank sold the funds primarily to wealthy clients of its private bank.

Credit Suisse is arguing in court filings that Softbank knew more about a financial injection into Katerra late last year. The deal saw Greensill relinquish the $440 million – unbeknownst to Credit Suisse, according to the bank's legal filings. 

Poised For U.K. Lawsuit

The Greensill fund disaster represents Credit Suisse's most pressing legal and regulatory problem. The bank has vowed to explore any avenue to recoup client money, after getting stuck at just north of 70 percent of the funds' volume before Credit Suisse pulled the plug in March.

Though the discovery was lodged in the U.S., the bank expects to sue Softbank in U.K., the «FT» reported, citing a source. A spokesman for Credit Suisse, which is deliberating how public to be with its Greensill failings, didn't comment.