The midfielder has unsurprisingly come in for criticism from Republic of Ireland supporters, but Southgate believes Rice showed maturity in making his decision, adding that he feels the youngster is one of the best of his age group in the Premier League.
"It has been a well publicised situation with Declan and we have tracked him for a long time".
"It's increasingly the case, if you look at our under 16s over 50 percent of them have dual nationality and some could play for more than two countries", he said.
"We always want to play in a way that excites people, we want a team that the public are proud to watch and we hope to play our part".
"I think it's easy to be vocal when you haven't walked in those shoes", the England boss said.
Southampton pair Alex McCarthy and Angus Gunn will no doubt be taken into consideration for future squads if one of them can establish themselves as the undisputed first-choice at St Mary's, while Dean Henderson - on loan at Sheffield United from Manchester United - was also mentioned by Southgate.
"As I said last month, I had an extremely difficult decision to make regarding my worldwide future, but I have made that decision and now I just want to focus on the future, continuing to work hard and play as well as I possibly can". That said, there was never any guarantees made to him.
"His character and leadership qualities mean he fits in very well into the way that we work".
Elsewhere, Jordan Pickford keeps his place in the squad despite some question marks over his recent form for club side for Everton.
None of those matches were competitive fixtures, however, and Gareth Southgate has opted to pick the English-born 20-year-old in his squad for the game against the Czechs at Wembley on March 22 and the trip to Montenegro three days later.
The squad also sees a return for Burnley goalkeeper, Tom Heaton, who hasn't played for England since June 2017, while defenders Danny Rose, James Tarkowski, Harry Maguire all return after the injuries which caused them to miss England's last game, which was a 2-1 win over Croatia in the UEFA Nations League in November.
"But when I look at Jordan, his performances with us have been excellent".
"We're pleased with what Jordan's done and we've got to help him through what was hopefully a blip at the weekend".More news: Game of Thrones Final Season Episode Runtimes Are Shorter Than You Thought
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