FRANKFURT — Deutsche Bank, the ECB and its biggest investor sought to reassure shareholders and staff of its financial strength on Friday after S&P cut its rating and questioned its plan to return to profitability.

Shares in Deutsche Bank closed at an all-time low on Thursday as past misadventures in high-risk investment banking haunted new Chief Executive Christian Sewing’s attempt to refocus on its more staid corporate banking roots.

A source familiar with the thinking of the European Central Bank (ECB), which regulates Deutsche Bank, and its top shareholder HNA Group Co Ltd [HNAIRC.UL] of China, separately said they backed management’s strategy of retrenchment.

This followed a report on Thursday that the U.S. regulator viewed the lender as “troubled” last year, and on Friday a Standard & Poor’s credit rating downgrade to BBB+ from A-.

Deutsche Bank shares were up 3.7 percent at 1235 GMT, although the cost of insuring against default .

Meanwhile in Australia, federal prosecutors were preparing criminal cartel charges against Deutsche, as well as the country’s third-largest bank and Citigroup, over a $2.3 billion share issue. All deny wrongdoing.

Sewing, a Deutsche Bank ‘lifer’ appointed in April after the removal of former CEO John Cryan, said in a letter to staff: “At group level, our financial strength is beyond doubt”.

But the newsflow was “not good”, Sewing added as S&P questioned his ability to get Deutsche Bank back to profit after three years of losses by scaling back its global investment bank and refocusing on Europe and Germany.

“We see significant execution risks in the delivery of the updated strategy amid a continued unhelpful market backdrop, and we think that, relative to peers, Deutsche Bank will remain a negative outlier for some time,” S&P said