Countries in Britain's Commonwealth have given formal approval for a bill ending male preference in the line of succession to the throne.

Deputy Prime Minister Nick Clegg pledged Tuesday that the law would be changed as soon as possible.

The measures were agreed on by prime ministers of the 15 countries of the Commonwealth that recognize Britain's Queen Elizabeth as their head of state.

The new law, once enacted by Britain's parliament, will mean that the first child of Prince William and his wife, Catherine, will be born a future king or queen in waiting. St. James's Palace on Monday announced that the royal couple — known as the Duke and Duchess of Cambridge — are expecting a baby.

The child will displace Prince Harry as the third in line to the throne, coming behind Queen Elizabeth's eldest, Prince Charles, and his son, Prince William.

For centuries, preference was given to male heirs, so a first-born princess could be overtaken in line by a younger brother.

Catherine's pregnancy was announced on Monday, after she was hospitalized for acute morning sickness. Palace officials say she is feeling better but will stay in the hospital for several days. They say she is less than 12 weeks pregnant. No due date has been announced.

William married the former Kate Middleton on April 29, 2011, at Westminster Abbey in a ceremony viewed by an estimated worldwide audience of 2 billion.