Gremio have confirmed Arthur's long-awaited move to Barcelona is on the brink of being completed.
Barca have reportedly been keen on the midfielder since he shone in Gremio's Copa Libertadores triumph.
Arthur was photographed wearing the Catalan club's jersey in a meeting with Barca sporting director Robert Fernandez in December.
The deal has been edging towards completion for some time and Gremio president Romildo Bolzan says the move is imminent.
"The topic is on its way to being finished," Bolzan told reporters after Gremio's match on Wednesday.
"The documents are not signed yet, but the transfer is reaching the final phase.
"I think it will be over by tomorrow or the day after tomorrow.
"Some things still depend on legal issues. It still requires some care.
"It is heading towards a final situation tomorrow, I believe."
Barca, who signed South American players Philippe Coutinho and Yerry Mina in the January transfer window, are expected to close a deal worth an estimated €40million for Arthur.