WASHINGTON - US President Barack Obama on Monday extended his congratulations to British Prince William and his wife Kate for the birth of their first child.

"(First lady) 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," the president said in a statement, using the royals' official titles.

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

On Monday afternoon, Kate gave birth to a boy, who is now 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."