The US units of Deutsche Bank and Banco Santander failed US stress tests while 30 others passed, the US Federal Reserve said on Wednesday after markets had closed.

Established in the wake of the 2008 financial crisis, the test calls on banks to carry enough capital to "act as a cushion to absorb losses and help ensure that banking organizations have the ability to lend to households and businesses even in times of stress," the Fed said in a statement.

Deutsche Bank Trust Corp failed for the second year in row, and Santander Holdings USA missed the mark for the third consecutive year.

The US central bank said Deutsche Bank showed "some improvements in certain aspects of capital planning (but) the firm overall continues to have material unresolved supervisory issues that critically undermine its capital planning process."

However, the chief executive of Deutsche Bank USA, Bill Woodley, assured that its "capital adequacy … has never been in doubt."

"We appreciate the Federal Reserve's recognition of our progress, and we will implement the lessons learned this year in order to strengthen our capital planning process," Woodley said in a statement.

Meanwhile, Santander Holdings USA CEO Scott Powell said the bank has already launched preparations for next year's stress test.

"We are well on our way to making the enhancements necessary to improve our qualitative assessment," Powell said in a statement.

Thirty other financial institutions passed, including Bank of America and JPMorgan Chase, while Morgan Stanley was asked to resubmit its plan by the end of 2016.

ls/sms (Reuters, AFP, dpa)