The matches are April 20-21.
The winner will return to the top-tier World Group in 2020 with a chance to win the Fed Cup title. The loser will drop down to World Group II next season.
The U.S. is 8-0 against Switzerland in the Fed Cup, but the nations' most recent meeting came in 1993.
The No. 8-ranked Stephens was the 2017 U.S. Open champion and No. 14 Keys was the runner-up there. Kenin, Pegula and Brady are all also ranked in the top 80.
Switzerland's roster has no one ranked higher than No. 81 Viktorija Golubic.