Boro will argue that Dong-gook has only missed games because he has been injured, when they apply for a work permit this week.
The South Korean will increase the competition for places up front, but he will find it hard to displace Yakubu and Mark Viduka, who have scored 13 goals between them in the last 10 games.
In other transfer news it is believed that Boro will lodge a bid for Colchester defender Greg Halford who is highly thought of as the best right back in the country outside the Premiership.
There has been little progress on the move for West Brom's Zoltan Gera or Benfica's Maunel Fernandes who spent the first half of the season on loan at Portsmouth.
On the exit front Fabio Rochemback and Massimo Maccarone are no closer to leaving the Riverside while Ugo Ehiogu is attracting interest from Rangers.