The Duke and Duchess of Cambridge are expected to tour the Caribbean in honour of Queen Elizabeth's Platinum Jubilee.
The couple are set to mark the monarch's 70 years on the throne by taking a trip that would have "a focus on ecological issues", with Belize - where the queen is head of state - likely to be among their stops.
Representatives for Prince William, who once trained with the Welsh Guards in Belize, and his wife Catherine were seen last week on the Central American nation's island Ambergris Caye in what was described as an "advance party" ahead of an official visit in the spring.
A source told the Mail on Sunday newspaper: "Their people were very secretive and kept saying this had to be kept very quiet, but on a small island like Ambergris Caye it's impossible to keep anything quiet for very long.
"They were talking about a four-day visit to Belize in March as part of a longer trip to this part of the world. They said William and Kate might visit the Caye and also go to mainland Belize. It's all anyone here is talking about. We are so excited."
Last year, Belize's Prime Minister John Briceno refused to rule out his nation following Barbados in removing the queen as head of state.
He said: "We need to find what fits Belize best."
Prince Harry was the last high-profile royal visitor to the nation, taking a trip in 2012 to mark the queen's Diamond Jubilee.
It is likely the Belize trip for William and Catherine - who have children Prince George, eight, Princess Charlotte, six, and two-year-old Prince Louis together - will form part of a bigger Caribbean tour of other Commonwealth nations such as Jamaica, Trinidad and Tobago, St. Lucia, and St. Kitts and Nevis.
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