Obama, Kevin Rudd congratulate British royals on new birth

US President Barack Obama has congratulated Prince William and his wife Kate on the birth of their first child.

"Michelle and I are so pleased to congratulate the Duke and Duchess of Cambridge on the joyous occasion of the birth of their first child," Xinhua quoted Obama as saying in a statement.

"We wish them all the happiness and blessings parenthood brings," he added.

On Monday, Kate gave birth to a boy, the third in line to the British throne. She wed William in April 2011, and was confirmed pregnant last December.

"The child enters the world at a time of promise and opportunity for our two nations," Obama said.

"Given the special relationship between us, the American people are pleased to join with the people of the United Kingdom as they celebrate the birth of the young prince," he said.

Meanwhile, Australian Prime Minister Kevin Rudd and Governor-General Quentin Bryce Tuesday sent their country's congratulations to Prince William and Kate.

The birth of a baby is an experience to celebrate and cherish, Bryce said in a statement.

"On behalf of all Australians, I send heartfelt congratulations to the Duke and Duchess of Cambridge on this joyful occasion. We wish the new parents every happiness and send warm greetings of welcome to the little prince," she said.

Rudd said it was a happy day for the nation's close friends in Britain and across the Commonwealth.

"On behalf of all Australians, Therese and I extend our warmest regards to the new parents, Prince William, Duke of Cambridge, and Catherine, Duchess of Cambridge," he said in a statement.

"We share in the joy of the Royal Family, particularly Prince Charles on the birth of his grandson and Queen Elizabeth II on the birth of her great-grandchild."