Gyan to join Al-Ain on loan
"Anyone who has seen Asamoah play will know that he hasn't been himself in recent months. This option suits all parties at the present time and the club is well-protected in the deal," Bruce said in a club statement on Saturday.
Bruce, who hopes to have Gyan back at the Stadium of Light firing on all cylinders next term, said on Friday that hopes of a move to a big club had affected one of the best players from the 2010 World Cup.
"All the parasites, as I call them, hover around. People are in his ear constantly trying to engineer a deal for him," Bruce said.
Sunderland lost main striker Darren Bent to Aston Villa last season and successful loan signing Danny Welbeck is now back at Manchester United.
Bruce has brought in forwards Niklas Bendtner, South Korea's Ji Dong-won and Connor Wickham in recent months.