Barcelona still needs at least 100 million euros ($102 million) to be able to register new additions and comply with the requirements of the Spanish league, newspaper Sport said on Saturday, citing club sources.

Barca had previously admitted to having serious financial problems and yet have splashed the cash this pre-season, with Poland's Robert Lewandowski from Bayern Munich the most eye-catching purchase for a fee of around 50 million euros.

Even Bayern coach Julian Nagelsmann has openly wondered how the maths work given their debts are a reported 1.35 billion euros.

Barcelona sold a further 15% of TV rights for the next 25 years to investment firm Sixth Street on Friday having already ceded 10% at the end of June.

The deal has made a difference but Sport says they need to go further to satisfy Spanish league finance rules, which were part of the reason why they had to let Lionel Messi leave for Paris Saint-Germain last year.

Barca want to sell a minority stake of no more than 49.9% in their Barca Licensing and Merchandising (BLM) unit, Sport reported, adding that the current United States pre-season tour will net 10 million euros.

Selling a player such as Frenkie de Jong to Manchester United could offer another partial solution, although Catalan media reports say Barca want to sign another player – with Athletic Bilbao centre back Iñigo Martinez eyed.