Both clubs are desperate to strengthen their defences with the Gunners pursuit of Shkodran Mustafi, 24, hitting a brick wall due to Valencia’s demand for a £30m fee for the German international.
With time and options running out, Arsene Wenger is prepared to take Fonte as an experienced but short-term solution.
Jose Mourinho meanwhile is looking for a similar player to nurture Eric Bailly, 23, as he settles into English football.
Signed from Villarreal earlier in the summer, the Ivory Coast international has made two impressive starts for United but Mourinho believes Bailly would benefit from the presence of a player who knows his way around English football.
With the transfer window closing in a fortnight’s time, United are prepared to offer Marcos Rojo, 26, as a makeweight in the deal to bring the Portuguese international to Old Trafford.
The Argentinian has failed to impress Mourinho during the summer and is one of eight first team squad members that the Portuguese wants to release from his squad.
Southampton want to keep Fonte, a member of Portugal’s winning Euro 2016 team, and have offered him a new contract which would take him to the top of the St Mary’s pay league.
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