The two London clubs have reached deadlock in their negotiations because Arsenal are unwilling to match Fulham’s £4 million valuation of the 37-year-old goalkeeper.
Arsenal had a £2m bid rejected for Schwarzer in May and have not made a further offer, although it is understood that the two clubs are still in talks.
“They have different valuations of Schwarzer,” a source close to the transfer told Goal.com.
“Arsenal don’t want to pay the £4m that Fulham want but one possibility is a player exchange deal to push it through."
It is understood that several Arsenal fringe players have been mentioned and Fulham, who are keen to bolster their forward ranks despite the signing of forward Moussa Dembele from AZ Alkmaar on Wednesday, have enquired about Vela among others.
Arsenal are likely to value the Mexican international far beyond a £2m makeweight, even though the 21-year-old is running out of time to make his mark at the club.
A deal has also been held up because the west Londoners have been unable to secure a proven goalkeeper to replace Schwarzer. An offer was made to David James but the former England No.1 made the surprise decision to drop a division and move to Championship club Bristol City.
Vela has made more appearances for his country than he has for Arsenal in the Premier League (25, including only three starts) and has scored just eight goals for the club since his 2006 switch from his homeland, although he did spend two seasons on loan in Spain.
Despite the sticking points in Arsenal’s pursuit of Schwarzer, who handed in a transfer request last week and was not picked for Fulham’s opening Premier League fixture against Bolton Wanderers, both sides expect the deal to eventually be completed before the end of the transfer window.
Fulham manager Mark Hughes is continuing to look at forward options after his pursuit of Craig Bellamy failed.
Hughes has been widely linked with a move for another forward he managed at Manchester City and Blackburn Rovers, Roque Santa Cruz, but sources say he is not expected to pursue the Paraguayan because of concerns over his injury record.