Rangnick has succeeded Ole Gunnar Solskjaer until the end of the season before moving into a two-year consultancy role at the club.
"If everything goes well I might make the same recommendation that I did at RB Leipzig twice - that it might be a good idea to keep working with me for one year - but it is all hypothetical," said the 63-year-old German.
Rangnick was at Old Trafford on Thursday to watch United beat Arsenal 3-2 in the Premier League and his first game in charge will be at home against Crystal Palace on Sunday at 14:00 GMT.
"The people with whom I have spoken have been very clear we are speaking of a six-month role as manager," he said.
"We have never spoken about what will happen in the summer.
"Right now, I'm fully aware that they might be looking for a new manager. If they will then speak with me about that, we will see.
"For me, now it is about winning the next games and this is the major focus."
What about Ronaldo?
Portugal forward Cristiano Ronaldo scored twice in the win over Arsenal but there have been questions over whether the 36-year-old will fit in under Rangnick's pressing style of play.
"Seeing Cristiano in the second half at the age of 36, amazing - top professional. At his age, I have never seen a player who is still that physically fit and he is still a player who can easily make the difference.
"It's about how we can develop the whole team, it's not only about Cristiano. We play in the most competitive league in the world so we need all the players on board. What I saw from Cristiano, he is more than willing to do that."
Rangnick takes over with United seventh in the Premier League, 12 points behind leaders Chelsea, and through to the Champions League last 16 as Group F winners.
He added: "The challenge is to bring more balance into the team. Even [against Arsenal] we needed three goals to win the game. It's almost two goals on average conceded per game and this is too much.
"The game was exciting for the fans but as the coach they are not the games you need every day."
'We haven't spoken about new players'
Solskjaer had been in charge at United since December 2018 but was sacked on 21 November, having won only one of his final seven league matches. He failed to win a trophy during his tenure.
Rangnick said he spoke to the Norwegian for 90 minutes last weekend, while he also met with caretaker manager Michael Carrick to try to convince him to stay on.
Carrick took over after Solskjaer's dismissal and was in charge for a win over Villarreal, draw at Chelsea and the victory against Arsenal before announcing he was leaving the club.
"I had a private conversation with him for more than an hour. I tried to persuade him to stay on board. In the end, I had to accept his decision," said Rangnick.
"I will try to find a few people who can join us in the next one or two weeks but, because of Brexit regulations, it is not that easy. Many of my former colleagues are in long-term contracts with big clubs so are not available right now."
Rangnick has left his role as head of sports and development at Russian club Lokomotiv Moscow to take up the job.
He has built an impressive coaching reputation during his time in Germany, with both Liverpool boss Jurgen Klopp and Chelsea manager Thomas Tuchel speaking highly about their compatriot.
He set Ulm on course to promotion to the Bundesliga for the first time before spells in charge of Stuttgart, Hannover, Hoffenheim, Schalke and RB Leipzig.
He won the German Cup with Schalke in 2011 and took RB Leipzig to the final in 2019.
During the 2010-11 season, he led Schalke to the semi-finals of the Champions League, where they lost 6-1 on aggregate to United.
On his philosophy, he said: "I think to gain control on games in the future, it has to do with playing proactively.
"It is about helping the team play together. It is about togetherness, team spirit - the two halves [on Thursday] were completely different and having these unique fans behind us will help us.
"It is not easy, I cannot do it in a few training sessions. It's about control - this is the major target."
Rangnick will meet the United players on Friday, when those who did not play against Arsenal will train, before all the squad have a training session on Saturday prior to the Palace game.
He has already been linked with bringing in players during the January transfer window but said that was not his main focus at the moment.
"We haven't spoken about new players," he said.
"Now is the time to get to know the current squad in detail. The squad is definitely not too small. There is enough players.
"Maybe after Christmas there will be a time to speak about possible transfers in the winter. In my experience, it is not the time for sustainable transfers."
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