Both Premier League rivals are believed to be in the race to sign the Argentine international, but talkSPORT report that the Serie A outfit - managed by former Reds boss Rafael Benitez - are increasing their efforts to bring him to Italy and want to secure such a deal before he travels to this summer's World Cup.
Given his extensive experience and reliability, it isn't particularly difficult to see why so many clubs appear keen to sign Mascherano.
The 29-year-old has been a crucial figure for the Catalan giants since 2009, initially providing crucial protection in midfield before forging a defensive partnership with Gerard Pique in the absence of talismanic captain Carles Puyol.
However, it appears as if his five-year stint at the Nou Camp is about to come to an end, with reports emanating from Spain in recent times having suggested that Mascherano was one of a number of players - also including the likes of Cesc Fabregas and Dani Alves - set to be made available for transfer.
The prospect of a reunion with former boss Benitez must presumably hold a great deal of appeal for the player, as must the chance of a potential return to Anfield with Liverpool - the club he left to join Barcelona.
Manchester United's interest in Mascherano is slightly more surprising, although it becomes perhaps less so when you consider that new manager Louis van Gaal - who will take the reins at Old Trafford in a full-time basis following the World Cup - will require strengthening both in the centre of midfield and defence.