The 28-year-old has failed to settle with Benfica since joining from Arsenal de Sarandi in 2013, having made just 28 league appearances for the Portuguese giants.
Benfica loaned the central defender out to Getafe for the 2013-14 campaign and he has started just once in Primeira Liga this season.
Newcastle have been monitoring Lopez’s situation for some time and it’s understood that they made an approach for his services last January.
Rafael Benitez made clear his frustrations at a lack of financial backing over the summer and he is hoping the board will provide him with the funds to pursue Lopez again when the winter window rolls around.
The Argentina international is currently contracted to Benfica until the summer of 2021, however, they are likely to allow him to leave if Newcastle make a decent offer.