"We felt it was in the best interests of the player in relation to his football career that he moved to Middlesbrough on loan for the remainder of the season. Danny has never expressed an intention to leave Leeds United and he has asked for this to be put on record.
"He will now concentrate his efforts on giving 100 per cent commitment to his new club and he is looking forward to the challenge that is now ahead of him at Middlesbrough."
Mills could not risk losing his England place with the European Championships just around the corner and said: "Mr Eriksson had spoken to me saying that when it came to future international involvement, he really could justify considering me for squad inclusion only if I was playing first-team football.
"As much as I wanted to stay at Leeds, I also wanted regular first-team football. There is also the fact that I needed to take into account my future involvement with the England set-up.
"Everything now points to me playing in a Middlesbrough shirt for the first time against Leeds.
"Yes it will be tough for me but, if nothing else, at least I will have the chance to show Peter Reid what he will be missing out on."
United hope to have a near full squad to choose from for the trip to the Riverside.
Lucas Radebe has recovered from the pain in his knees that forced him to miss Tuesday night's draw with Southampton and should return to the defence.
Midfielder Jody Morris was forced off against the Saints with a knee injury but has recovered and will keep his place in midfield. Frazer Richardson and Ian Harte also suffered knee injuries in the same game but are expected to be fit.
Middlesbrough are expected to also give Spanish World Cup star Gaizka Mendieta his first home appearance after an impressive debut in the midweek draw at Leicester. Manager Steve McClaren has injury worries over defenders Chris Riggott (back) and Colin Cooper (groin).