Hillary Clinton criticised Barack Obama last night for his willingness to meet with some troublesome world leaders during a debate featuring questions posed through Youtube.
The CNN debate featured video questions submitted from around the world through the website to the top 2008 Democratic contenders.
The format was designed to force candidates to drop their rehearsed answers and sound bites. It sparked lively exchanges between all eight Democratic candidates on Iraq and diplomacy, and an extended discussion of race and gender involving Mr Obama and Ms Clinton.
Hillary Clinton
Ms Clinton said she was proud to be running as a woman, and Mr Obama, an Illinois senator who would be the first black president, said Americans were ready to go beyond racial divisions.
"I couldn't run as anything other than a woman," Ms Clinton said. "I'm excited that I may be able finally to break that hardest of all glass ceilings."
Mr Obama said he would be willing to meet with leaders of Iran, Syria, Venezuela, Cuba and North Korea.
The candidate, who leads Democrats in fundraising and is looking to cut Ms Clinton's lead in polls, said it was important to search for areas "where we can potentially move forward" and added: "I think it's a disgrace that we have not spoken to them."
Ms Clinton, the New York senator, disagreed, saying such meetings could be used as propaganda purposes. "Certainly, we're not going to just have our president meet with Fidel Castro and Hugo Chavez and, you know, the president of North Korea, Iran and Syria, until we know better what the way forward would be," she said.
Asked if Muslim leaders in the Middle East would be able to negotiate and work with a woman, Ms Clinton said that after meeting various foreign leaders as first lady in the 1990s: "There isn't much doubt in anyone's mind that I can be taken seriously."
More than 2,000 video questions were posted on YouTube's site for the debate. CNN editors used more than 30 of them. The candidates also submitted their own videos.