The 26-year-old, who has been out of international duties for almost a year, signed a one-year loan deal from Porto after struggling to command a starting place last season.
Waris was a second half substitute on Saturday when Nantes suffered a 3-1 defeat to Monaco.
"The desire and passion to play for my country at the next Africa Cup of Nations is equally a reason to come here," Waris told BBC.
"Playing for Ghana is always an honour. Playing with Nantes would give me the opportunity to do it in Cameroon with Ghana," he added.
Waris boasts of 22 international caps with four goals since making his debut with the Black Stars in 2012.