The Queen may miss the annual New Year's Day church service at Sandringham, with a decision expected to be taken on Sunday morning on whether she is well enough to attend.
The 90-year-old monarch has not been seen in public for 11 days since she and Prince Philip fell ill with what was officially described as "heavy colds".
The illness forced the Queen to miss the Christmas Day service at St Mary Magdalene church in Sandringham for the first time in 28 years.
Philip, 95, who is known for his robust health, was well enough to attend and walked briskly to the church as usual on Christmas morning with Prince Charles, Prince Harry and other family members.
But a Buckingham Palace spokeswoman said she was unable to confirm or deny if the Queen would be going to the 16th century church today on New Year's Day, adding: "The Queen is continuing to recover from her heavy cold and is still in residence at Sandringham."
"We probably will not know what is happening until the morning."
If the Queen does attend church, it is possible she will be joined by Prince William and wife Kate who spent Christmas with the Middleton family in Berkshire.
The Queen and Philip are believed to have spent most of the last week staying indoors together at Sandringham House in north Norfolk.
It is thought the Queen has not been seen going around the 20,000-acre Royal estate in Norfolk as she often does when in residence.
However Prince Philip is said to have joined other members of the Royal family on their traditional Boxing Day pheasant shoot.
The Queen and the Prince were forced to cancel their plans to travel up to Sandringham on December 21 at the last minute due to their illness.
The couple, who traditionally spend their Christmas and New Year Break on the estate, were due to catch a train as usual from London to King's Lynn.
But police who were waiting for them at King's Cross station and in King's Lynn were stood down shortly before their train was due to leave.
Instead the couple were flown directly from Buckingham Palace to Sandringham by helicopter the following day.
The 110 twin-engined Sikorsky S-76C helicopter from The Queen's Helicopter Flight with a top speed of 178mph took just 40 minutes to make the 110 mile flight.
Buckingham Palace was forced to confirm that the Queen had not died this week after hoaxers announced her 'death' in a fake BBC Twitter account.