Fitch noted that persistent budget deficits mean the debt-to-GDP ratio "will continue to increase in the coming years and peak at 97 percent in 2019," compared to the median level of 42 percent for AA-rated economies.
"The high debt burden limits France's ability to respond to future shocks," the agency cautioned in a statement.
However, "France's prudent debt management strategy helps mitigate the risks from its high public debt."
In addition, Fitch said French President Emmanuel Macron's ambitious structural reform program has coincided with solid growth.
The outlook for France's debt rating is stable, which means Fitch does not see any developments on the horizon that are likely to lead to a change.
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