"I'm proud to be president of the United States," Biden told his supporters at the Iowa State Society inauguration ball.
The audience laughed as Biden's son Beau, Delaware's attorney general, corrected his 70-year-old father and told the crowd he had misspoken.
Biden, who is known for making gaffes during US presidential campaign, quickly corrected himself. "I'm proud to be vice president of the United States," he said, "but I am prouder to be Barack Obama's, President Barack Obama's, vice president."
Biden committed several gaffes in his political career. During 2008 campaign, in a speech Biden pointed out Missouri state Senator Chuck Graham and invited him to stand up to address the crowd. Unfortunately, Graham was wheelchair bound.
The Democrat leader, who will be close to his 74th birthday on the next election day in 2016, has not ruled out the possibility of running for the White House.Biden was administered the oath of office on his family bible by the Supreme Court Associate Justice Sonia Sotomayor at a private ceremony at his official residence in Washington on Sunday, following a private mass.