The Portuguese, who won two Premier League titles with Chelsea in 2005 and 2006, said it did not matter which Premier League club he would return to despite his affection for the Blues.
"I cannot deny what is clear in my mind. After Real Madrid, England. That is for sure," the former Porto and Internazionale coach told Sky Sports.
Asked which team he would like to join, he added: "In England, everyone. I'm a blue, I'm a London blue but I'm a professional."
The idea of replacing Alex Ferguson at Manchester United, who has been in charge since 1986 and was due to retire in 2002 but changed his mind, has long appealed to the confident Portuguese manager.
Chelsea remain his true love though and he has previously stated he will return to Stamford Bridge one day.
Mourinho fears they will badly miss striker Didier Drogba this term after the Ivorian, matchwinner in the Champions League final in May, left for Shanghai Shenhua.
"I believe Drogba is a big difference to them. You can't replace Drogba," he said, aware that Fernando Torres has been hit-and-miss so far this term as Chelsea's lone striker.
"Chelsea will miss Drogba and it will mean a few points less."
Mourinho's Spanish champions have had a sticky start to the season, losing two of their four La Liga games before a stirring comeback to beat Manchester City 3-2 late on in Tuesday's Champions League encounter.
The Portuguese lashed out at his players following last weekend's league defeat by Sevilla, questioning the commitment and focus of many of his team.
He surprisingly dropped Spain defender Sergio Ramos for the City thriller, replacing him with little-used 19-year-old Rafael Varane which led to media speculation that one of the leading figures in the dressing room had been punished.
"I am not going to talk about him (Ramos) because he didn't play the last game," Mourinho said.
"Pepe and Varane played, they played very well and kept things simple. They were good in the air, they were quick and they pushed the team up the pitch. City scored two goals against us but neither of the central defenders was at fault."
Pressed on the reasons for Varane playing instead of Ramos, Mourinho snapped back: "I can explain why Ramos didn't play, but I want to ask you a question.
"Why don't you speak about Varane? A week ago, why didn't you talk about the sadness of Varane and his frustration at not being able to play?
"Now he plays a good game and no-one speaks about him. You tell me this and I will happily tell you about Ramos."
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