Sunderland were expected to up the ante for Souttar after seeing a £400,000 bid for the 17-year-old rejected during the summer.
The two clubs are understood to have been in contact ever since and have now reached an agreement over an initial £600,000 payment, plus a hefty sell-on clause for the centre-half.
Sunderland are the only club who have made a concrete bid for Souttar, who has made 14 first-team appearance since he was handed his debut last January.
Saturday October 5
12:45 Manchester City v Everton
15:00 Cardiff City v Newcastle United
15:00 Fulham v Stoke City
15:00 Hull City v Aston Villa
15:00 Liverpool v Crystal Palace
17:30 Sunderland v Man Utd
Sunday October 6
13:30 Norwich City v Chelsea
13:30 Southampton v Swansea City
16:00 Tottenham v West Ham United
16:00 West Brom v Arsenal
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