No further details about Queen Elizabeth's condition are provided with the message, except for a written statement stating that the Queen "is in good spirits and disappointed that she is no longer able to visit Northern Ireland", reports AP.
The decision comes just days after the queen was seen walking with a cane in connection with a public event in London.
Buckingham Palace adds that the Queen "sends her warmest greetings to the people of Northern Ireland and that she looks forward to a visit in the future".