Arsenal's bid for Valencia defender Christian Mosquera has been rejected by the LaLiga side as they have set their asking price for the Spanish youngster.
The Gunners have entered talks for Mosquera, 20, as they look to find suitable cover for first-choice options William Saliba and Gabriel.
While Mikel Arteta's go-to pair have become one of the Premier League's strongest defensive partnerships in recent seasons, Arsenal appear intent on strengthening their back-line depth.
Such a move by Arsenal may have been prompted by the hamstring injury Gabriel suffered in April, along with a recognition that adding another high-calibre centre-back would give them the chance to occasionally rotate Saliba.