Lack of concentration killed Beijing's chances
The Chinese club led until the 88th minute of the contest but were overrun by a more desperate Jets outfit who scored twice in the closing stages to take the points.
"The result is very disappointing for me but I am satisfied with our players," Lee said after the match.
"They tried their best and gave a good performance during the game.
"During the first half some of our players played without confidence especially in controlling the ball. At half-time I requested them to be confident and focus more on attack.
"But with the intensity of the AFC Champions League and the Chinese Super League, our players were really tired and they had a problem with concentration."