The New York senator made her comments in the first Democratic radio address since Obama became the party's nominee, The Hill reported.
"I speak to you today as a proud Democrat. A proud American. And a proud supporter of Barack Obama," Clinton said. "The contrasts between us and the Republicans could not be starker, especially on issues that matter to middle class families."
Clinton also used the radio address to criticize Arizona Sen. John McCain, the presumptive Republican nominee.
"Next week, John McCain and the leaders of the Republican Party will hold a convention that offers a starkly different vision for our nation: continuing in the same direction we're headed now," Clinton said.
"The choice in this election is as clear as the stakes are high. I urge all of you to join us in supporting the great ticket of Barack Obama and (vice presidential nominee) Joe Biden, and help elect Democrats in Congress who will work with them."