Brindisi - Top-ranked Serena Williams fought back from a set down to win her windy singles match over Sara Errani, but couldn't produce another victory in the decisive doubles encounter as Italy beat the United States 3-2 on Sunday in a Fed Cup World Group playoff.
Brindisi native Flavia Pennetta and Errani defeated Williams and Alison Riske 6-0, 6-3.
It was Williams' first career loss in the Fed Cup, dropping to 16-1 - 13-0 in singles and 3-1 in doubles.
Earlier, Williams put together an error-filled 4-6, 7-6 (7/3), 6-3 win over Errani before Pennetta routed 65th-ranked Christina McHale 6-1, 6-1.
Italy return to the World Group and can compete for the Fed Cup trophy next year while the US were relegated to World Group II.