Britain's Queen Elizabeth II will sign a new Commonwealth charter Monday, which includes language many have interpreted as tacit support for gay rights.
It will be the 86-year-old's first official engagement since leaving the hospital where she was treated for a stomach bug last week.
In a televised ceremony, the monarch will make a symbolic pledge for equal rights for people in the 54 countries in the British Commonwealth.
A statement from the palace said the Commonwealth Charter will declare: "We are implacably opposed to all forms of discrimination, whether rooted in gender, race, color, creed, political belief or other grounds."
Sources have said the queen will stress that the rights must "include everyone," which is seen by many as an implicit nod to equal opportunity and an end to discrimination against the gay and lesbian population, the Daily Mail reported.
ABC News royal contributor Victoria Arbiter said it is the first time the Queen has shown her support for gay rights in her 61-year reign.
"That's a big step," said Arbiter.
"The queen has to remain politically neutral.... While we won't hear her personal views on this, the fact that she is endorsing it publically in front of television cameras, it really does speak volumes."
British newspaper columnists have described the queen's decision to highlight gender equality and gay rights as a "watershed" moment.
The charter is still only a symbolic step for many of the British Commonwealth countries, because homosexuality is still illegal in 41 of the 54 nations, BBC News reported.
Earlier Monday the queen was forced to cancel her morning attendance at the Commonwealth Observance at Westminster Abbey, because she was reportedly not yet well enough.
A royal source told the Telegraph: "She is at the tail end of the gastroenteritis. When you're 86 it takes longer to get over gastroenteritis than when you're younger.... It's a matter of pacing herself, her condition hasn't worsened at all but she is still recovering."
The palace said the Queen was on track to attend a gathering of Commonwealth leaders Monday evening, where she will sign the historic charter.