Withdrawing Maguire from the squad five hours later, he said: “As I said earlier today, I reserved the right to review the situation.
“Having spoken to Manchester United and the player, I have made this decision in the best interests of all parties and with consideration of the impact on our preparations for next week.”
What is the other squad news?
Southgate has given first call-ups to Manchester City midfielder Phil Foden, Manchester United striker Mason Greenwood and Leeds midfielder Kalvin Phillips.
Forward Danny Ings and goalkeeper Dean Henderson are also in the squad.
Southampton’s Ings, who has been capped once, scored 22 Premier League goals last season, one behind Golden Boot winner Jamie Vardy. Uncapped Manchester United keeper Henderson spent last term on loan at Sheffield United and helped them finish ninth in their first season back in the top flight.
Captain Harry Kane has been selected despite the Tottenham striker having been in quarantine following a trip to the Bahamas.
Midfielder Jack Grealish, who helped Aston Villa retain their Premier League status last season, has not been included in the 24-man squad.
Forward Raheem Sterling has been picked along with his Manchester City team-mate Kyle Walker, who is recalled.
Liverpool’s Jordan Henderson and Alex Oxlade-Chamberlain and Leicester duo Ben Chilwell and James Maddison miss out through injury.
England face their Euro 2016 conquerors Iceland in Reykjavik on 5 September before playing Denmark in Copenhagen three days later.
The disruption caused to the football calendar by coronavirus, including Euro 2020 being delayed by a year until 2021, means England have not played since November 2019, when a 4-0 win in Kosovo concluded their Euro 2020 qualification campaign.
Trio rewarded for impressive seasons despite disruption
Foden, 20, has earned his senior England call-up after impressing for Manchester City last season, playing 38 games in all competitions and scoring eight goals.
Greenwood, 18, burst on to the scene last season, scoring 17 goals. That is a joint record for a teenager in a season for Manchester United, alongside George Best, Brian Kidd and Wayne Rooney.
Defensive midfielder Phillips, 24, caught the eye in helping Leeds win promotion to the Premier League after 16 years in the second or third tiers.