The final U.S. rules for systemically important banks provide clarity on the additional capital these banks will have to hold, but raise new questions, too, says a new report from Fitch Ratings.

Recently the U.S. Federal Reserve issued its final rules on the capital buffers that will be required of U.S.-based globally systemically important banks (GSIBs). The final rules clarify which banks qualify as a GSIB, and define the key inputs that will determine how the buffers will be set, Fitch’s report says

However, the rules mean it’s likely that U.S. GSIBs will be required to hold more capital than their foreign counterparts, the Fitch report notes.

The Fed’s approach includes two methods to calculating the necessary capital cushions for GSIBs, with banks required to use the higher of the two results; which “is expected to keep GSIB buffers elevated relative to some non-US regimes for the foreseeable future,” the Fitch report says.

Moreover, the rules “leave open the potential” that the buffers will be included as minimum hurdles that the banks must meet as part of the Fed’s annual stress testing exercise, the Fitch report indicates.