Manchester United chiefs Richard Arnold and John Murtough have flown to Barcelona in an effort to iron out the issues with the Frenkie de Jong deal.
The club's new manager Erik ten Hag has made the signing of the 25-year-old Dutch midfielder his No 1 priority this summer.
United agreed a £46.5 million deal in principal to sign De Jong a fortnight ago but the move has stalled over a contractual issue between the player and the Camp Nou giants.
De Jong agreed to defer his salary during the coronavirus pandemic in 2020, with the wages due to be repaid to him over the next four years to help the Catalan club as they struggled financially because of the loss of income.
The player is reluctant to leave Barcelona until he is paid what he feels is due.
But United chief executive Arnold and football director Murtough have now flown to Barcelona to try to break the impasse - rather than travelling with the squad to Thailand for the club's friendly against Liverpool in Bangkok on Tuesday.
It is reported that they are holding talks with Barca's director of football Mateu Alemany, managing director Rafael Yuste and sporting adviser Jordi Cruyff to try to get the deal done.
Ten Hag was asked about De Jong on Monday as his squad prepared for the meeting with old rivals Liverpool.
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"We know what we want," said Ten Hag. "We only want new players, we want the right new players. My first press conference, I already said definitely we are searching for players in midfield."
After the Liverpool game, United fly to Australia for games against Melbourne Victory on July 15 and Crystal Palace on July 19.