Fabian Schar has completed his medical at Newcastle and is expected to finalise his move on Thursday, according to Sky sources.
Sky Sports News understand Newcastle activated his £3m release clause at Deportivo La Coruna yesterday.
Newcastle are looking to replace Chancel Mbemba, who they sold to Porto for £7m earlier this month and have been tracking Schar, who won three Swiss titles with Basel, for some time.
The 26-year-old left Basel to join Hoffenheim in 2015 where he made 30 appearances before joining Deportivo last year.
He has played 42 times for Switzerland and was a key figure as they reached the last 16 of the World Cup in Russia.
Rafael Benitez told Sky Sports News on Tuesday that he was confident of adding to his squad before the transfer window closes on August 9 saying: "We will do something and we have to do something".
So far this summer, Newcastle have made goalkeeper Martin Dubravka's loan from Sparta Prague permanent for £3.6m.
They have signed Sung-Yeung Ki on a free transfer from relegated Swansea, while Kenedy has returned to St James' Park on loan from Chelsea after a successful stint during the second half of last season.
Newcastle begin their Premier League camapaign at home to Tottenham on August 11, live on Sky Sports.