Miller has failed to make an impact at Middlesbrough since joining the club from Aberdeen in January.
“If Rangers ask the question, I would be forced to make the toughest decision of my career,” Miller told the Daily Record.
“It is flattering to be linked with a club as big as Rangers. It is also nice to know clubs are taking a keen interest in what I am doing.
“I have been linked with Rangers for most of my career, but have never kicked a ball for them.”