File Photo: A Buckingham Palace handout image released on September 23, 2022, shows King Charles III carrying out official government duties from his red box in the Eighteenth Century Room at Buckingham Palace, London on September 11, 2022. AFP
Britain's new monarch, who took the throne when his mother Queen Elizabeth II died last month, had intended to deliver a speech at the November 6-18 gathering, the Sunday Times reported.
But the plan has been axed after Truss -- who was only appointed prime minister by the late queen two days before she died -- opposed it during a personal audience with Charles at Buckingham Palace last month.
The report comes amid speculation Britain's new leader, already under fire over her economic plans which have sparked market turmoil, could controversially scale back the country's climate change commitments.
Her newly assembled cabinet contains a number of ministers who have expressed scepticism about the so-called 2050 net zero goals, while Truss herself is seen as less enthusiastic about the policy than her predecessor Boris Johnson.
The Sunday Times said she is unlikely to attend COP27 -- the 27th Conference of the Parties to the UN Framework Convention on Climate Change (UNFCCC) -- at the Egyptian resort of Sharm el-Sheikh.
Britain hosted the last summit in the Scottish city Glasgow, when Charles, the late queen and his son William all addressed the event.
Both Downing Street and Buckingham Palace declined to comment on the report.
The newspaper said the episode was "likely to fuel tensions" between Charles and Truss, but cited a government source who claimed the audience had been "cordial" and there had "not been a row".
Meanwhile, a royal source told the paper: "It is no mystery that the king was invited to go there.
"He had to think very carefully about what steps to take for his first overseas tour, and he is not going to be attending COP(27)."
Under convention in Britain, all overseas official visits by members of the royal family are undertaken in accordance with advice from the government.
However, despite not attending in person, reports said the king still hopes to be able to contribute in some form to the conference.
Charles III is a committed environmentalist with a long history of campaigning for better conservation, organic farming and tackling climate change.