The Blues will discover who they will face in the southern section of the competition on Friday, with the draw scheduled for (1pm).
Thailand-based energy drinks company Carabao take over the sponsorship of the League Cup from Capital One.
And the draw will take place from the company’s Bangkok headquarters.
France 1998 World Cup winner, Emmanuel Petit, will pick the teams out of the pot – alongside Football League chief executive Shaun Harvey and Britain’s ambassador to Thailand, Brian Davidson.
Seventy teams will be in the first-round draw, with 36 in the southern section.
Matches will take place the week commencing August 7.
With Kenny Jackett’s outfit unseeded, it means they could face the likes of Reading, Norwich or Aston Villa.
The new Pompey boss could also return to former clubs Millwall or Wolves, who are also seeded.
The Blues were knocked out of the competition at the first hurdle last season, after losing 3-2 at Coventry following extra-time.
Curtis Main and Kal Naismith were on the scoresheet for the visitors, but Andy Rose’s extra-time goal sent Paul Cook’s men crashing out.
Pompey have failed to make it beyond the second round of the competition since the 2010-11 campaign.
Steve Cotterill’s outfit reached the third round after beating Stevenage 2-1 in the first stage in the southern section, before defeating Crystal Palace 4-3 on penalties at Fratton Park.
The game ended 1-1 after 120 minutes.
Pompey hosted Leicester in the third round but lost 2-1.
The Blues have never got past the quarter-finals of the competition since it began in 1960, having reached the last eight six times.
Despite the 2009-10 season being one of the most miserable in Fratton history, Avram Grant guided Pompey to two cup runs.
Along with reaching the FA Cup final, there was also a quarter-final appearance in the League Cup.
A 3-1 win at Carlisle and a 4-0 thrashing of Stoke on home soil set up a last-eight clash with Aston Villa.
The Blues took the lead through a Stiliyan Petrov own goal after 10 minutes.
But Emile Heskey ensured Villa were level two minutes later and they went on to win the game 4-2.
– WILL ROONEY