World number three Federer and number four Wawrinka will team up with Marco Chiudinelli and Michael Lammer, 167th and 454th respectively in the ATP rankings.
Federer and Wawrinka had already confirmed that they planned to take part in the September 12th-14th matches in Geneva, but Luethi's official announcement was required to make that formal.
Tennis watchers had been left guessing about the remaining names, however.
"Marco Chiudinelli has been in greater and greater shape over the past few months and he's worked flat out to get ready for these semi-finals, so he deserved his slot in the team," Lüthi said in a Swiss Tennis statement.
There had been suggestions that Lüthi would call up Swiss number four Yann Marti, who stands 209th in the ATP rankings.
"I've followed Yann Marti's recent rise with a lot of satisfaction, he's made a lot of progress," said Lüthi.
"But what's at stake is too important to start experimenting with new players."
He said he expected Italy to deploy a team exclusively of players from the ATP top 100, including world number 17 Fabio Fognini,49th-ranked Andreas Seppi, plus Paolo Lorenzi and Simone Bolelli, respectively 78th and 85th.
"This isn't going to be a walk in the park, and it's going to be all the more important to be buoyed up by our fans," said Lüthi.