Goal reported last week that the Gunners were in advanced talks for the centre-back with the Brazilian's agent in London to try to finalise a deal worth up to £15 million for the Villarreal defender.
Wenger, speaking after Arsenal's 3-2 win over Brighton in the FA Cup, now expects confirmation of Gabriel's arrival to come on Monday.
When asked on reports the deal is close, Wenger told reporters: "They are accurate, it's very very very close. It should be done I think tomorrow."
"[He is] a player who's 24 years old, good size, good pace and a good defender. He plays for only one year in Europe so maybe there are some things to work on but the potential is there."
There have been concerns over Gabriel's work permit application to play in the Premier League having yet to feature for Brazil at any international level, but Wenger is confident of no hold-ups in completing the move.
He added: "We will be alright on that front."