Wall Street banks saw their fixed-income trading revenues pressured in the fourth quarter of 2013, and their capital markets businesses remain subject to uncertainty in 2014, according to a new report from Fitch Ratings.

In a special report published Tuesday, the rating agency says that revenues from fixed income, currency and commodities (FICC) trading were “challenged” for the large U.S. banks and securities firms in Q4. This, in turn, limited the growth in capital markets revenues, it notes. Overall, aggregate capital markets still accounted for 29% of consolidated revenues, Fitch says.

For the year ahead, Fitch says “lingering regulatory, economic and political uncertainty will be key drivers of activity levels.”

For example, the firm says that it believes that if the upcoming U.S. debt ceiling is not addressed in a timely manner, “the resultant market uncertainty could contribute to a further reduction in capital markets activity in the first quarter.”

“Conversely, a more substantial improvement in economic conditions and market sentiment could spur increase volumes and M&A activity,” it notes.