The return to Europe's premier competition is worth in excess of £100 million in revenue and gives United the financial platform to pursue multiple signings in the same window.
The plan, as understood, is to spend around £80 million on a marquee central midfielder, approximately £40 million on a replacement for Manuel Ugarte if the Uruguayan can be sold at a reasonable price, and a further £20 million on a third midfield option.
Baleba, 22, had been United's primary target since last summer, when they made contact with Brighton and balked at a £100 million valuation. His form has dipped this season and the club believe the price may prove more negotiable, though Brighton remain in a strong negotiating position with the Cameroonian under contract until 2028 or 2029.
Nottingham Forest's Elliot Anderson had been considered United's number one target earlier in the season, but they are increasingly reluctant to match Forest's valuation, which is understood to exceed £100 million. Manchester City, who do not have the same budget constraints, are considered frontrunners for Anderson.
Adam Wharton of Crystal Palace, Newcastle United's Sandro Tonali — though interest has cooled slightly — and Aurélien Tchouaméni of Real Madrid, who is understood to prefer staying at the Bernabéu, complete the primary list. West Ham's Mateus Fernandes and Bournemouth pair Alex Scott and Tyler Adams fall into the second tier of targets at the lower price point, alongside Wolverhampton Wanderers' Joao Gomes, who is certain to leave the relegated club this summer.
Southampton's Shea Charles has also been monitored as a third, cost-effective option to supplement the squad, reports the Daily Mail.
The midfield rebuild is one element of a broader summer that also requires a left-sided forward, left-back, central defender and reserve goalkeeper.
On the outgoings side, United hope to generate significant fees from the sales of Rasmus Hojlund, Marcus Rashford, André Onana, Ugarte and possibly Joshua Zirkzee, while freeing up wage space by releasing Casemiro, Jadon Sancho, Tyrell Malacia and Altay Bayindir.
Fabrizio Romano confirmed United's interest in Atalanta's Ederson as a potential backup if preferred targets prove too costly, noting the Brazilian is available for around €40-45 million. Manchester United's decision on their primary target is expected to be made quickly, with the club keen to complete at least one marquee signing before the World Cup begins in mid-June.