Kane last week hinted that he would be open to leaving Spurs if he felt as though they were no longer on track to win silverware, alerting the attention of United as well as Real Madrid and Manchester City.
Tottenham are unlikely to let their talisman leave for anything less than £150m, though, and Carragher believes that such a sum for a player who will be 27 by the time next season starts could cause the Red Devils to think twice.
"Kane turns 27 in July. We have no idea when the next transfer window will open or next season start. If Kane does not leave soon, the situation gets trickier for him," Carragher wrote in his column from The Telegraph.
"When players hit 28, psychologically it makes a big difference to clubs. They see him as nearer 30, recognise there is no resale value and balk at high valuations. Manchester United's need for a top-class number nine is urgent and they might see Kane as the ideal fit, but they will apply the same logic if the fee is upwards of £150m.
"In other circumstances, the Tottenham striker's comments suggesting he would consider a move in the near future would be reasonable. Spurs fans may not like it, but I can understand why Kane is wondering whether his trophy ambitions will be served elsewhere."
Kane is Tottenham's third-highest goalscorer of all time with 181 goals in 278 appearances for the club. body check tags ::