According to sources close to the situation, Wissa held urgent talks this week with Brentford's director of football, Phil Giles, after flying back early from the club's pre-season training camp in Portugal. During the meeting, the 28-year-old is said to have made his frustrations clear and reiterated his desire to join Newcastle, who have already had an initial bid rejected.
The DR Congo international is understood to believe that Brentford are going back on a previous agreement to allow him to leave should a reasonable offer be submitted. The perceived U-turn has left Wissa "infuriated," according to those close to the player, and prompted him to issue a stark warning: permit the transfer or risk losing him entirely.
Brentford have yet to accept an offer from Newcastle, but talks are ongoing. It is understood that further discussions have taken place in the past 24 hours between Giles and Newcastle's acting sporting director, Andy Howe, as the Magpies explore ways to get a deal over the line.
Despite the impasse, a resolution remains possible, with sources suggesting that both clubs are still open to negotiation. Newcastle remain keen to bolster their attacking depth ahead of the new season, and Wissa - who scored seven Premier League goals last term - is high on their list of targets.
Brentford, meanwhile, are facing growing pressure to either sanction the sale or find a way to reintegrate the forward into Thomas Frank's plans ahead of the Premier League opener.