Ferdinand missed out on the England captaincy this week when Fabio Capello plumped for John Terry.
Ferdinand's position at United is number three behind Gary Neville and Ryan Giggs.
And while there is no immediate end in sight to that situation, Ferguson has assured the Londoner he will eventually get the job on a full-time basis.
"The difference here is that I operate my captains on seniority.
"In the long-term Rio will be captain of Manchester United, there is no question about that. It is a position we are very comfortable with that.
"His leadership qualities have improved tremendously over the last couple of years and his ability is there for all to see."