Adam Webster has been pulled out of England duty to answer the Pompey SOS.
The 17-year-old received a maiden international call-up earlier this month after impressing for the Blues.
He was scheduled to take part in a four-team under-17 tournament in Portugal, which starts on Thursday.
But Michael Appleton was forced to veto the call-up, with Webster desperately needed by Pompey.
The defender has been a regular in the Blues squad of late, making two substitute appearances.
And with players expected to leave before tonight’s 11pm transfer deadline, Pompey could ill-afford losing a member of their paper-thin squad to England commitments.
Appleton said: ‘Adam has been pulled out of the England squad.
‘I just think we are a little bit thin on the ground for him to go there.
‘He will get plenty of opportunities to go and play for England. I’m sure he will get other call-ups.
‘From my point of view, I don’t think we are in a position where we could allow him to go and possibly play in those games.
‘He understands that and his parents are also aware of the reasons why.
‘The most important thing at the minute is Portsmouth Football Club and he’s a big part of that, regardless of him just turning 17.
‘I think you’ve seen in the two short performances what he can do.
‘He might have to play in the coming months.’
England head coach John Peacock has now replaced Webster in his squad.
The Algarve Tournament will see England under-17s face top-quality opposition in Portugal (February 2), Holland (February 4) and France (February 6).