Blackstone chief executive officer Stephen Schwarzman said Fitch Ratings had ample reason to downgrade long-term U.S. debt. The ratings agency cut the U.S. rating to AA+ from AAA on Tuesday, citing concerns over mounting debt and a lack of “confidence in fiscal management.” The downgrade from Fitch was the first since Standard and Poor made a similar move in 2011. Schwarzman agreed with the reasoning behind the Fitch downgrade. “The numbers justify it, regrettably,” Schwarzman told CNBC’s “Squawk Box ” on Friday. “We’ve had an explosion of debt since the global financial crisis, and we don’t appear to have a lot of discipline going forward.” Schwarzman added that the U.S. remains the supplier of the world’s reserve currency, which should provide some confidence to investors who might otherwise view the downgrade with concern. “The U.S. is the U.S. – we are the reserve currency, [and] we do defend a large part of the world, including people who have AAA’s, “Schwarzman said. “When there’s crisis in the world, they buy our securities.” Schwarzman cautioned, however, that the ratings change is nonetheless a “shot across the bow.”