Belgium will play France in the Davis Cup final after coming back from 2-1 down to beat Australia in Brussels.
Australia had the overnight lead but world number 12 David Goffin narrowly overcame 20th-ranked Nick Kyrgios 6-7 (4-7) 6-4 6-4 6-4 as Belgium levelled.
Steve Darcis then saw off Jordan Thompson 6-4 7-5 6-2 for victory.
France booked a place in the final, which they will host, when Jo-Wilfried Tsonga beat Dusan Lajovic to give them an unassailable 3-1 lead over Serbia.
"It's a big win for me and a big win for us," said Darcis.
"David [Goffin] did an unbelievable job for us today. I have never seen him play as well as this and I'm really happy I could finish it off."
Nine-time champions France will play 2015 runners-up Belgium on 24-26 November.
Yannick Noah's side needed only one singles match on Sunday to see off a Serbian side who were without Novak Djokovic.
Underdogs Serbia had picked up an unexpected first point when Lucas Pouille lost to Lajovic in Friday's singles but Tsonga levelled by beating Davis Cup debutant Laslo Djere.
Pierre-Hugues Herbert and Nicolas Mahut then beat Filip Krajinovic and Nenad Zimonjic in the doubles and Tsonga's second victory saw them progress.
Meanwhile Davis Cup holders Argentina were relegated from the world group after losing 3-2 to Kazakhstan in Astana on Sunday.
Mikhail Kukushkin beat US Open quarter-finalist Diego Schwartzman 6-4 6-4 7-6 (7-2) to give the home team an unassailable 3-1 lead.
Argentina become the third team in history to be relegated a year after winning the title and will play in the Group One Americas zone next year.
The 2016 winners were without Juan Martin del Potro and Federico Delbonis, who opted not to play having helped their country to win the final against Croatia.
"We've got to let some time pass and think what each one of us could have done better... those of us who came here and those who didn't," said world number 28 Schwartzman.
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