United States join Kazakhstan and France in qualifying for Billie Jean King Cup finals
The United States, who have won more titles than any other nation in the competition with 18, went into Saturday with a 2-0 lead after teenager Coco Gauff (19) beat Julia Grabher (26) 6-1 6-3 and Pegula secured a 6-0 7-5 win over Sinja Kraus (20).
Pegula beat Grabher 6-1 6-3 on Sunday to seal the tie, while Gauff and Caty McNally (21) bested Melanie Klaffner (32) and Kraus 6-1, 6-4 in the doubles.
The best-of-five qualifiers featured two singles matches on Friday and two reverse singles plus a doubles rubber on Saturday.
Wimbledon champion Elena Rybakina (23) had helped Kazakhstan build a 2-0 lead on Friday and the world number seven had no trouble dispatching Magda Linette (31) 6-4 6-2 to give her side an unassailable lead in Astana.
Rybakina's compatriot Yulia Putintseva (28) was scheduled to play in the fourth singles rubber which was not played but she teamed up with Anna Danilina (27) in the doubles.
Poland, without injured world number one Iga Swiatek, finally got on the board as Weronika Falkowska (22) and Alicja Rosolska (37) won 6-3 6-4 in what was essentially a dead rubber.
In Coventry, Britain were no match for France as WTA Finals champion Caroline Garcia (29) ended the home team's challenge by beating Harriet Dart (26) 6-1 6-7(10) 6-1 to give them a 3-0 lead.
After a one-sided opening set which lasted less than half an hour, Dart took encouragement from the home fans in the arena and rallied in the second set tiebreak where she saved two match points.
But the intense second set had taken its toll on Dart, who ran out of gas in the third as Garcia broke early when another double fault from the Briton handed her a 2-0 advantage.
Garcia got the double break and the world number five served out the set to secure France's place in the Finals.
"It was a great match, a great battle," said Garcia, who spent more than three hours beating Katie Boulter on Friday.
Italy were leading 2-0 after Friday's play in Bratislava thanks to wins for Camilla Giorgi (31) and Martina Trevisan (29) but they changed their singles line-up on Saturday and almost slipped up.
Anna Karolina Schmiedlova (28) kept the tie alive by beating Jasmine Paolini (27) before Viktoria Hruncakova (24) beat Elisabetta Cocciaretto (22) to set up a tense doubles decider.
Slovakia fell just short though as Cocciaretto and Trevisan beat Hruncakova and Tereza Mihalikova (24) 6-4 4-6 7-5.
Ukraine were 2-0 down to the Czech Republic after Friday's rubbers and Marta Kostyuk (20) halved the deficit when she came from behind to beat former French Open champion Barbora Krejcikova (27) 3-6 6-1 6-4.
However, Marketa Vondrousova (23) wrapped up the tie for the Czechs with a 6-3 6-4 win over Katarina Zavatska (23) as the teams opted not to play the doubles match.
Germany booked their place in the finals by sealing a 3-1 victory over Brazil after Friday's rubbers were shared.
Jule Niemeier put the Germans ahead with a 7-6(3) 3-6 6-2 defeat of Brazil's Beatriz Haddad Maia (26) before Anna-Lena Friedsam thrashed Laura Pigossi (28).
Spain were never troubled by Mexico as they took a winning 3-0 lead on Saturday in Marbella, Nuria Parrizas-Diaz (31) securing the winning point by beating Marcela Zacarias (29).
Two of the nine qualifiers were still to be decided with Slovenia versus Romania locked at 2-2. A doubles decider was suspended midway through the first set due to inclement weather and organisers planned to resume the contest on Sunday.
Leylah Fernandez (20) bounced back to defeat Ysaline Bonaventure (28) 4-6 7-5 6-2 and give Canada a 2-1 lead over Belgium to roars of approval from the home crowd in Vancouver.
Belgium's Greet Minnen (25) then knotted the match with a three-set win over Katherine Sebov (24). But Fernandez and Gabriela Dabrowski (31) left no doubt about the doubles outcome, defeating Minnen and Kirsten Flipkens (37) 6-1, 6-2.
The 12-team finals will be contested in November when Switzerland, who were exempted to the finals alongside runners-up Australia, will attempt to retain their title.
The nine triumphant teams from the qualifiers go forward along with one 'wildcard'.
No venue has yet been announced.