Wayne Rooney has said he never contemplated joining Manchester City as he finally issued a public apology to supporters of Manchester United.

The striker said he wanted to "apologise for my side of things" as he reflected on the contract dispute that led to him asking for a transfer, only to change his mind when the club offered him a five-year deal that made him the best-paid player in their history. The suspicion at Old Trafford was that Rooney's head had been turned by the enormous riches on offer at City, but Rooney argued that was not the case. "Everyone is saying that I was definitely going to Man City," he said. "Believe me, if I had gone it wouldn't have been in England."

That throws up the possibility Rooney was eyeing a move to Barcelona or, more likely, to join José Mourinho at Real Madrid, whose president, Florentino Pérez, has made it clear he would love to sign the man who scored 34 goals for United last season.

Rooney did not say whether he had been aware of negotiations with City – his agent, Paul Stretford, has a close relationship with the club's football administrator, Brian Marwood – and is acutely aware some United supporters still believe he acted with traitorous disloyalty. At one point a group of 30 people had turned up at his house, brandishing a banner that read: "If you join City you're dead."

The length of time it has taken for him to say sorry has not helped, with Ferguson publicly stating on 22 October that an apology was forthcoming. Rooney said: "I feel like I have apologised to the fans, but everyone keeps saying that I haven't and, if that is the case, then I apologise for my side of things.

"I have made my point clear since I signed my contract that I am committed to this club for the long term and I want to be successful with this club. I spoke with the manager and [the chief executive] David Gill and they reassured me the club was moving forward and, from that point, it took only two or three hours to negotiate my contract and sign it."

Rooney marked his first United start for two months by scoring the decisive penalty that saw them beat Rangers 1-0 at Ibrox last night to qualify for the Champions League's knockout stages.

"It will give me confidence," he said. "It was nice to score but the main thing was to get back playing because I don't think I have consistently had a run of games this season. People are saying how badly I have been playing but I don't think I have played that many games for my form to have been a disaster.

"With everything that has happened, [the criticism] all goes a bit overboard but I know myself I have been through patches before when I haven't played well and come through them. I know 100% I will come through this one."

Rooney was asked for his reaction when he heard that Ferguson was sending him to Nike's headquarters in Portland, Oregon, for a week-long training camp to improve his fitness. "Well, I wasn't going to argue with him," he replied. "I needed to get in the training and, if that is what they wanted me to do, I was happy to do it.

"I am just happy it is all over now and I want to put it behind me and look forward. Mentally I have been OK. I am mentally strong but because the football has not been going well, and the other things that have happened in my personal life, everyone has put it down to me not being mentally strong. I am, but the most important thing for me is to get back playing and score goals. I want to get back to the standard of last season.

"I am a confident person and I think I can do it. You see so many players leave this club and not do so well so I am just delighted I have stayed."