Qualification for the mixed-gender team tournament is based on the rankings of nominated players.
Djokovic is expected to instead make his return to action on Australian soil in Adelaide.
The Serbian has seen a three-year visa ban overturned on review and will be allowed to make a bid for a tenth Australian Open title early next year.
"It's a relief, obviously knowing what I and people closest to me in my life have been through this year with what happened in Australia and post-Australia obviously," said the Serb.
"I could not receive better news for sure - during this tournament as well. The Australian Open has been my most successful grand slams. I made some of the best memories there.
"Of course, I want to go back there, I want to play tennis, do what I do best, hopefully have a great Australian summer.
"I'm always thankful to go through experiences, no matter what the experiences are. I try to be optimistic and positive in life. I look forward to starting the new year in Australia, and we'll see how the next year goes."
Djokovic's absence from the United Cup has taken some of the luster off the new tournament.
The team event starts just four days after Christmas on 29 December and will make the 2023 campaign a real marathon.
The Adelaide International 1 takes place from 2 January and will be followed by another event at the same venue in the second week of the year.
Thanks to the United Cup, the Sydney ATP 250 tournaments fall away.
Running parallel to the two Adelaide International ATP 250's will be the Pune and Auckland events which are of the same level.
The Australian Open occupies the second and third weeks of the 2023 calendar and will be followed by a week of Davis Cup qualifiers.
We are likely to see a far more active Novak Djokovic during the first three months of the year.
However, there is still some doubt surrounding Djokovic taking part in North American events ahead of the Sunshine Double in March.
While Australia has dropped vaccination against Covid-19 from its entry requirements, those restrictions still remain in place in the United States.
Either way Djokovic is expected to have a much better lead in to the clay court season provided he can stay injury free, and it could be a big year on the Grand Slam front for the GOAT contender.