Willian has instructed his agent to press ahead with his move from Chelsea to Barcelona this summer, according to reports in Spain.
The 29-year-old is currently preparing for Brazil's World Cup quarter-final against Belgium on Friday but has already decided that he wants to leave Stamford Bridge.
Mundo Deportivo report that Willian has told Kia Joorabchian, one of his main representatives, that he is determined to join Barcelona.
Willian, who is also on Manchester United's shortlist, is also said to be confident that Joorabchian will be able to reach an agreement with Chelsea.
Joorabchian is currently in London and is speaking to Chelsea's hierarchy in order to persuade them to sell the Brazilian midfielder to Barcelona.
Chelsea are demanding £70 million for Willian but Barcelona have no plans to match their valuation.
The Spanish champions are also hopeful that Willian will personally push for a move away from Stamford Bridge.
United launched a late bid to sign Willian last summer and Mourinho, who managed the Brazilian at Chelsea, is still looking to bolster his attacking options and is expected to make a move before the start of the new season.