The centre-back's contract is set to expire at the end of next season and reports suggest that talks have yet to take place over an extension at Old Trafford.
Smalling's situation has led to talk that fellow Premier League side Arsenal are interested in taking the former Fulham man to the Emirates Stadium.
However, the England international insists he is committed to United.
"That [my contract] is one that I have not really discussed with anyone," he said ahead of England's friendly against Italy on Tuesday.
"The manager is showing his faith in me and, if I am playing, I'm happy.
"We have got another eight games, so we will look to finish as strong as we can.
"I do [see my long-term future at United]. I am enjoying it, I have always enjoyed playing for United, especially at the minute.
"If I can contribute, as now, then I am happy to stay as long as they want me."
Smalling has made 18 Premier League appearances for Louis van Gaal's men this term and looked particularly impressive in the wins over Tottenham and Liverpool in the club's last two outings.
Manchester United report: Antony's future has already been decided after new comments from CEO
‘Slot hasn’t come in and changed everything, making it all about himself – it’s been about the players he’s inherited, getting the best out of a system he likes’: Liverpool manager impressing former players with personality and tactical approach
