(Reuters) - Global ratings agency S&P affirmed its "AA+" long-term and "A-1+" short-term unsolicited sovereign credit ratings on the U.S. on Thursday, and kept the outlook on the long-term rating as 'stable'.

"A diversified and resilient economy with solid growth, extensive monetary policy flexibility, and benefits associated with the unique status as the issuer of the world's leading reserve currency underpin the U.S. sovereign rating," S&P said.

It expects the Federal Reserve System, which provides the U.S. with considerable monetary policy flexibility, to navigate the challenges of lowering domestic inflation and addressing financial market vulnerabilities.

Earlier in the month, peer Fitch affirmed United States' long-term foreign currency sovereign credit rating at "AA+" with a "stable" outlook.