The United goalkeeper recently told ManUtd.com he would love the chance to play for Great Britain in the Olympic Games, the rules of which require most footballers to be aged under 23.
"Obviously with Joe Hart doing so well in the [senior] England team, my chances might be few and far between in the future," said Amos.
"The Olympics would be a good opportunity to represent not just England but Great Britain at such a big event."
Amos is joined in the Under-21s squad by young Reds team-mate Will Keane, who could start alongside Bolton Wanderers striker Marvin Sordell, Aston Villa forward Nathan Delfouneso - currently on loan at Leicester City - or Sunderland's Connor Wickham.
The other keepers vying with Amos for a place in the eleven are Birmingham's Jack Butland - temporarily plying his trade with Cheltenham Town - and Middlesbrough shot-stopper Jason Steele.
England U21s versus Belgium U21s will be staged at the Riverside Stadium next Wednesday, 29 February, at 18:00 GMT. Tickets are available from Middlesbrough FC.