The Czech Republic beat Switzerland 3-1 to advance to its 10th straight Fed Cup semifinals on Sunday, and Serena Williams played her first competitive match in more than a year as defending champion United States defeated the Netherlands 3-1.
The Czechs, Fed Cup champions in five of the last seven years, travel to Germany, which made its first semifinals since 2015 after beating 2017 finalist Belarus 3-2 in Minsk. The US goes to France, which defeated Belgium 3-2.
Dual Wimbledon champion Petra Kvitova beat Switzerland's Belinda Bencic 6-2, 6-4 in the first reverse singles to give the Czechs an insurmountable 3-0 lead in the first-round match in Prague.
The second reverse singles was not played but Switzerland's Timea Bacsinszky and Jil Teichmann defeated lucie Safarova and Barbora Strycova 1-6, 6-4, 10-8 in the doubles.
The Germans last met the Czechs in the 2014 final, losing 3-1.
In Asheville, North Carolina, Serena Williams lined up alongside her sister Venus Williams in a doubles match.
Serena Williams had said her return to tennis would represent the "start of a long process." She and Venus lost 6-2, 6-3 to lesley Kerkhove and Demi Schuurs of the Netherlands.
The US already had clinched victory thanks to a pair of singles victories by Venus Williams and have an April 21-22 semifinal in France.
But this event was most notable for the return of Serena Williams, five months after giving birth. She hadn't played competitive tennis since winning the 2017 Australian Open.