Bristol have signed Argentina international Gaston Cortes.
The 26-year-old prop, who has four caps for his country, also represented Argentina Jaguars in the 2012 IRB Nations Cup.
Cortes is expected to receive visa clearance within 10 days but will not be available for Sunday's opening Championship game with Newcastle.
"He has international experience and plenty of potential to develop,"
Middleton told the club website.
"Gaston also brings the right type of mentality and attitude to the club. That's an important element in us investing in him."
Cortes added: "I am very excited about the move. I spoke to Liam a lot throughout the summer and he told me what he expects from a Bristol player.
"This is a great club with proud traditions. I am looking forward to playing in England and in the Championship next season."