Bellingham and Greenwood were high-profile omissions from the 23-man group named by Southgate on Friday (AEST), along with injured defenders Trent Alexander-Arnold and Harry Maguire.

Borussia Dortmund midfielder Bellingham has started all 10 games at club level this season and played an hour for England in their 4-0 win over Andorra earlier this month.

Greenwood has been used regularly by Manchester United this term, meanwhile, starting seven times and featuring from the bench on one occasion.

Bellingham's 802 minutes of playing time this term is the most of any England-qualified player in Europe's top five leagues when taking all competitions into account, while Greenwood's 634 minutes is the fourth-most of any United player.

Speaking at a news conference after announcing his squad, Southgate said: "They're both in similar situations, young players with heavy workloads at the moment.

"I've spoken to both of them. Jude at the moment is playing a high level of matches with Champions League games, league games. As an 18-year-old he had a full season last season and then into the Euros with no break.

"We have to remember these lads are still physically growing, so when we talk about young player development we have to be really careful in how we handle them.

"These are two players we think can be really exciting for England's future. We don't want to overload them, we want to make sure we are making the right decisions with them."

With Maguire missing out through injury, Milan centre-back Fikayo Tomori has been called up nearly two years since earning his one and only cap against Kosovo.

Tomori has helped Milan to nine clean sheets in Serie A since arriving at San Siro from Chelsea in January on an initial loan deal that has since been made permanent, a tally that has been bettered by only three others.

He also ranks 11th for successful passes among defenders in the Italian top flight over that period, which played a part in Southgate's decision to recall the 23-year-old.

"I like Fikayo in terms of his aggressiveness of defending," Southgate said. "Because he's got speed he's confident enough to defend on the front foot and he's improving on the ball as well.

"I have been very impressed. I thought he finished last season well. We were tracking him well last season and he is playing well this season. 

"He is at a club that's expected to win every week. I thought he did well against Liverpool and Juventus recently."

Reece James and Mason Mount have also been selected for the games with Andorra and Hungary over the next fortnight, despite missing Chelsea's 1-0 loss to Juventus in the Champions League on Wednesday as they continue to recover from injury.

Southgate explained: "They're clearly still to have appeared for their clubs so there's an unknown, but our understanding is Mason and Reece have a good chance for the weekend."

The other big news to come out of Southgate's penultimate squad selection of a memorable 2021 was the inclusion of Ollie Watkins and Aaron Ramsdale, the pair replacing Patrick Bamford and Nick Pope, respectively.

Ramsdale has made a positive start to life at Arsenal since ousting Bernd Leno as number one, his save percentage of 91.67 the second-best return of any keeper to have played at least three times for a team in Europe's top five leagues this term.

"Aaron was with us all summer and we had the opportunity to work with him for a long time and get to understand his strengths," Southgate said.

"Nick is still I think coming back from injury a little bit, but I think Aaron is just in a better vein of form at the moment.

"From Aaron's perspective, the move to a bigger club with higher expectations and a style of play where he is asked to build with his feet from the back, he's coping really well.

"I think that's an important factor for us when looking at the biggest matches, having a goalkeeper who has really adapted well to a move and is full of confidence."

England squad:

Sam Johnstone (West Brom), Jordan Pickford (Everton), Aaron Ramsdale (Arsenal); Conor Coady (Wolves), Reece James (Chelsea), Tyrone Mings (Aston Villa), Luke Shaw (Manchester United), John Stones (Manchester City), Fikayo Tomori (Milan), Kieran Trippier (Atletico Madrid), Kyle Walker (Manchester City); Phil Foden (Manchester City), Jordan Henderson (Liverpool), Jesse Lingard (Manchester United), Mason Mount (Chelsea), Kalvin Phillips (Leeds United), Declan Rice (West Ham); Jack Grealish (Manchester City), Harry Kane (Tottenham), Bukayo Saka (Arsenal), Jadon Sancho (Manchester United), Raheem Sterling (Manchester City), Ollie Watkins (Aston Villa).