Southampton could announce the club-record signing of AS Monaco striker as soon as Thursday.
The south coast have had a bid of £19.1 million accepted by Monaco, after initially failing with an offer of £13 million.
According to L’Equipe, terms have been agreed and official confirmation is expected within the next 24 hours.
The 26-year-old Argentinean has scored four goals in 15 Ligue 1 appearances so far this term, with 13 of those coming from the bench.
Southampton have only managed to score 24 goals in 24 Premier League games this season.