Richardson backed Obama despite his ties to Clinton and her husband, the former president. Richardson served as ambassador to the U.N. and as secretary of the Energy Department during the Clinton administration. Last month, Richardson and former President Clinton watched the Super Bowl together at the governor's residence in Santa Fe.

Richardson praised Hillary Clinton as a "distinguished leader with vast experience." But the governor said Obama

The Clinton campaign publicly dismissed the endorsement, after the New York senator failed to win it for herself.

Citing Clinton's victory in New Mexico in February, senior strategist Mark Penn said, "Perhaps the time when he could have been most effective has long since passed."

Richardson bristled at that statement, which he said was a stereotypical suggestion that he was only valuable in states with large Hispanic populations. "will be a historic and great president, who can bring us the change we so desperately need by bringing us together as a nation here at home and with our allies abroad."Obama wants Richardson to help boost his foreign policy credentials, which Clinton has described as lacking.

Obama said Richardson "frankly has more concrete accomplishments on the international stage than my opponents, Democrat or Republican."

Richardson was a roving diplomatic troubleshooter when he was a congressman from New Mexico, negotiating the release of U.S. hostages in several countries and meeting a rogue's gallery of U.S. adversaries, including Saddam Hussein and Fidel Castro.