The Premier League side are understood to have agreed the fee with the Glasgow giants, who are resigned to the fact that they will be unable to keep him in Scotland even though they’ve been handed a second chance in the Champions League qualifiers following their defeat by now disqualified Legia Warsaw.
Forster is set to negotiate personal terms with the Saints, where he is likely to become the fifth big signing of the summer following the arrivals of Graziano Pelle, Saphir Taider, Dusan Tadic and Ryan Bertrand – the latter on loan from Chelsea.
25% of the £10m fee will go to Newcastle due to a long standing clause inserted into the deal to take the now 26-year-old to the Bhoys in 2012.
The goalie’s imminent move to St Mary’s Stadium may free up Artur Boruc to leave, with the Pole said to attracting interest.
Forster went to the World Cup as a part of England’s squad, although he did not feature at any stage.