The Queen will "regretfully" not be attending COP26's evening reception in Glasgow in person.
Buckingham Palace made the announcement on Tuesday (local time).
"Her Majesty is disappointed not to attend the reception but will deliver an address to the assembled delegates via a recorded video message."
The Queen was due to make an appearance at the UN climate conference's reception on November 1.
The palace said since she was given advice to rest last week she had been undertaking "light duties" at Windsor Castle.
West of London, the Queen has spent much of her time at the castle since the onset of the Covid-19 pandemic last year.
COP26 is not the first trip she has cancelled recently.
She cancelled a trip to Northern Ireland last week following the medical advice.
The Queen also spent a night in hospital that week and was seen using a walking stick at a major public event when attending a Westminster Abbey service marking the centenary of the Royal British Legion, an armed forces charity.
She had previously been photographed using a cane in 2003, but that was after she underwent knee surgery.
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