Getty Images/Spencer Platt
The rating agency put US sovereign debt on its negative watch the last time things came down to the wire in October 2013.
Last week, Treasury Secretary Steven Mnuchin wrote Congress warning about the US federal debt situation the "extraordinary measures" the Treasury will have to take to continue funding the federal government if the debt ceiling is not raised by the deadline.
Fitch noted that a sizeable number of Republicans had opposed raising the debt ceiling in 2015 when the proposal was passed successfully with support from Democrats.
This time around, though, Fitch believes Republicans will offer lesser resistance as they are in control of both Congress and the White House.
The debt ceiling is expected to be raised to about $20 trillion.