West Ham U21s have been drawn into Pompey's EFL Trophy group.
The young Hammers will be making the trip to Fratton Park in Southern Group A, although dates are still to be confirmed.
Kenny Jackett's men are also set to meet League Two sides Colchester and Southend, with one game at home and the other away.
The opening round of group games are scheduled to be played in the week beginning September 7.
Pompey are the current holders of the competition following their penalty shoot-out victory over Sunderland in 2019.
They also made last season's final, but the Wembley contest with Salford was postponed due to the Covid-19 pandemic, with a new date yet to be confirmed.
|Southern Group A||Southern Group B||Southern Group C||Southern Group D|
|Colchester United||Crawley Town||Milton Keynes Dons||Bristol Rovers|
|POMPEY||Gillingham||Northampton Town||Oxford United|
|Southend United||Ipswich Town||Stevenage||Walsall|
|West Ham United U21||Arsenal U21||Southampton U21||Chelsea U21|
|Southern Group E||Southern Group F||Southern Group G||Southern Group H|
|Exeter City||Cheltenham Town||AFC Wimbledon||Burton Albion|
|Forest Green Rovers||Newport County||Charlton Athletic||Cambridge United|
|Swindon Town||Plymouth Argyle||Leyton Orient||Peterborough United|
|West Bromwich Albion U21||Norwich City U21||Brighton & Hove Albion U21||Fulham U21|
|Northern Group A||Northern Group B||Northern Group C||Northern Group D|
|Carlisle United||Morecambe||Bolton Wanderers||Port Vale|
|Fleetwood Town||Rochdale||Crewe Alexandra||Tranmere Rovers|
|Sunderland||Salford City||Shrewsbury Town||Wigan Athletic|
|Aston Villa U21||Manchester United U21||Newcastle United U21||Liverpool U21|
|Northern Group E||Northern Group F||Northern Group G||Northern Group H|
|Mansfield Town||Bradford City||Accrington Stanley||Grimsby Town|
|Lincoln City||Doncaster Rovers||Barrow||Harrogate Town|
|Scunthorpe United||Oldham Athletic||Blackpool||Hull City|
|Manchester City U21||Wolverhampton Wanderers U21||Leeds United U21||Leicester City U21|