United States President Barack Obama yesterday nominated judge Sonia Sotomayor to become America's first Hispanic Supreme Court justice, in his first opportunity to shape the country's powerful top tribunal.

Obama's selection of the 54-year-old Sotomayor, whose parents moved to New York City from Puerto Rico before her birth, is an exercise of one of the most significant powers the US Constitution grants the American chief executive.

Sotomayor would inject youth into the ageing liberal wing of the country's highest judicial panel. Justices serve until they retire or die, giving presidents an opportunity to influence policy long after they leave office. Obama's nomination is the first by a Democratic president in 15 years.

Picture of diversity

There is the possibility that Obama, before his four-year term is out, might be given the opportunity for more appointments, allowing him to reshape the court that has, in recent years, moved to the right with President George W. Bush's choice of conservative Justice Samuel Alito Jr.

The White House announcement ceremony was a picture of diversity, the first black president, appointing the first Hispanic Supreme Court justice, joined by Vice President Joe Biden, who is white.

Obama said he selected Sotomayor based on his search for a candidate with a "rigorous intellect" and "a mastery of the law" and one who recognised "the limits of the judicial role".

Sotomayor said "my heart today is bursting with gratitude" and called the nomination the "most humbling honour of my life".

Before selecting the nominee, Obama had said he was looking for a prospective high court justice who would bring "empathy" to the bench, a judge capable of understanding the effects of high court rulings on the lives of Americans.