Fitch Ratings placed the top-ranked US credit rating on rating watch negative Wednesday, reflecting the uncertainty surrounding the current debt ceiling debate and the possibility of a first-ever default.

The agency, one of the top three credit rating agencies along with Moody's and S&P, placed the US "AAA" on "rating watch negative," signaling that it could downgrade US debt if lawmakers do not agree on a bill that raises US Treasury's debt limit.

"The Rating Watch Negative reflects increased political partisanship that is hindering reaching a resolution to raise or suspend the debt limit despite the fast-approaching x date (when the U.S. Treasury exhausts its cash position and capacity for extraordinary measures without incurring new debt)," the company said in a statement.

However, Fitch added that it still believed there will be a resolution before the "X-date."

In 2011, S&P gave its first-ever credit downgrade to the US, cutting its rating to AA+. More than a decade later, that agency has still not restored its rating.

The warning from Fitch comes as Republican and Democratic lawmakers negotiate to raise the US debt limit, though no deal has been reached. Treasury Secretary Janet Yellen has said that the US may be unable to pay its bills as soon as June 1.

A US default could send shockwaves throughout the global economy and potentially cause a recession, according to experts.

Dow futures fell more than 85 points on Wednesday night, but the S&P 500 and Nasdaq traded in positive territory.