The K-League outfit has now given him green light to travel to England on 18th January.
"I thank manager Huh Jung-moo for allowing me to have a trial. I really want to become a Premier Leaguer," Koo said on The Korea Times.
The talented midfielder made his international debut at 18 against China at the East Asian Football Championships in 2008 and was a standout for South Korea at last year's Under-20 World Cup.
If a deal materialises, Koo will be the fourth South Korean currently playing in the Premier League, joining Manchester United's Park Ji-sung, Bolton winger Lee Chung-yong and Fulham's Seol Ki-hyeon.
Meanwhile, reports in France suggest Blackburn are ready to seal the signing of Stanislas Oliveira.
The Sedan midfielder is understood to have held talks with Rovers this week and is set to sign a three-year deal after the clubs reportedly agreed a deal worth around £500,000.
Source: Team Talk
Source: Team Talk