A leading record retailer says Robbie Williams and Nicole Kidman's duet is still on target to clinch the Christmas number one.
But HMV say Gordon Haskell's late bid could make it the closest contest ever.
Robbie's single has had the benefit of an extra day's sales over Gordon Haskell, but he is not far behind.
The chart positions are based on weekly sales figures from Sunday to Sunday.
Haskell released his single on Monday, whereas Williams' duet has already been out for a week.
HMV spokesman Gennaro Castaldo said: "I think it's fair to say the race is between Robbie and Nicole and Gordon Haskell.
"Robbie has had the benefit of an extra day's sales over Gordon Haskell but the newcomer isn't that far behind.
"Sales figures suggest it could be the closest run race for the Christmas number one of all time."
This year's Christmas number one will be announced on Sunday night.