FILE PHOTO: Christian Sewing, member of the board of Germany's Deutsche Bank is pictured in Frankfurt, Germany, February 2, 2018. REUTERS/Ralph Orlowski/File Photo

BERLIN (Reuters) - Deutsche Bank's DBKGn.DE sudden change in chief executive could prolong the lender's restructuring, ratings agency Standard & Poor's (S&P) said as it placed the bank on "credit watch negative" late on Thursday.

Last weekend retail banking specialist Christian Sewing replaced John Cryan as Deutsche’s CEO, raising the prospect of radical change at Germany’s flagship lender, which has been slower than rivals to reform after the financial crisis.

S&P said the placing of the bank’s “A-” long-term issuer credit rating on credit watch with negative implications reflected its view that the restructuring could now take longer and cost more than current expectations.

The agency affirmed its ratings on Deutsche Bank’s subordinated debt issues.

S&P said it believed that Sewing and the leadership team had the expertise to carry out the bank’s restructuring, adding that it would be better placed to assess the management’s strategy in coming weeks once Sewing’s priorities are known.

“This change could still act as a springboard for the bank to move more rapidly toward a sustainable, solidly profitable business model. However, in our view, it also implies that the bank may need to broaden the restructuring effort,” S&P said.

The agency said it would decide by the end of May at the latest whether to downgrade Deutsche Bank’s credit ratings once further details of the new leadership’s strategy are known.

Deutsche Bank said it respected S&P’s decision and appreciated the agency’s statement showing trust in the new leadership team.

“We note that this credit watch refers specifically to our preferred or structured senior debt and that Deutsche Bank’s other key ratings are reaffirmed,” it said.