Democrat Joe Biden and Republican congressman Paul Ryan traded barbs in the first and only vice-presidential debate of the 2012 election campaign on Friday.
Vice President Biden challenged Mitt Romney's running mate on a number of hot topic issues, such as the economy and foreign policy.
"War should always be the absolute last resort. There is no weapon that the Iranians have at this point," said Biden of Iran's alleged nuclear threat.
Obama's number two also criticised Romney's recently leaked speech that branded Democrat voters as victims.
"These people are my mum and dad, the people that I grew up with and my neighbours. They pay more effective tax than Governor Romney pays in his federal income tax," he said.
But Ryan defended Romney's secretly recorded video condemning the "47 percent" of the electorate that he said was dependent on government, calling it a mistake.
The Republican joked that the gaffe-prone Biden should understand that "sometimes the words don't always come out the right way."
The next presidential debate between Obama and Romney takes place on Tuesday evening in New York.
