It will "take some time" to change royal succession rules to allow a first-born daughter to take the throne, Prime Minister David Cameron cautioned today.
Pressure to scrap the 300-year-old law giving preference to male heirs has been increased because of Prince William's wedding to Kate Middleton later this month.
Mr Cameron and Deputy Prime Minister Nick Clegg are in discussions with other Commonwealth leaders about how to secure a change across the nations where the Queen is the monarch.
But with legislation required across the board, progress may be slow, he said.
"This has been discussed before and everyone in the front line of politics agrees that this does need to change and there are conversations ongoing," Mr Cameron told the Murnaghan show on Sky News.
"But it clearly does take some time because the Queen is not just Queen of the United Kingdom but many other countries around the world and so changes have to be changes that all countries take on board and put in place."
The thorny issue of primogeniture has occupied governments on and off for years - with individual MPs also making attempts to steer reforms through Parliament, most recently ex-Labour minister Keith Vaz in January.
At that time, Downing Street acknowledged that elements of the 1701 Act of Succession, which also bars Roman Catholics from succeeding to the throne, were "discriminatory" but said change would be "difficult and complex".
Mr Clegg said yesterday that the rules would appear to most people as "a little old-fashioned".
"My own personal view is that in this day and age the idea that only a man should ascend to the throne I think would strike most people as a little old-fashioned.
"And that if Prince William and Catherine Middleton were to have a baby daughter as their first child, I think most people would think it is perfectly fair and normal that she would eventually become Queen of our country."
Last month Prince William was urged by Labour MP and historian Tristram Hunt to "subtly show his support" for the reform campaign.