US vice president Joe Biden and Republican presidential hopeful Paul Ryan have engaged in a heated televised debate, dealing with terrorism, Afghanistan and abortion.
Mr Biden and Mr Ryan clashed over policy in Libya in the opening minutes of the vice presidential debate.
Moderater Martha Raddatz, a foreign affairs correspondent, opened the debate by asking if the attack on the US consulate in Benghazi was the result of a massive intelligence failure.
The US ambassador to Libya and three other Americans were killed in the attack.
Mr Biden called the deaths a "tragedy," and vowed that "we will bring to justice the men who did this."
In response, Mr Ryan said that "what we're watching on our TVs is the unravelling of the Obama foreign policy."
As the debate moved on to the issue of a nuclear-armed Iran, Mr Biden said his administration had the toughest sanctions in history, even as his Republican rival says the White House has no credibility on the issue.
Mr Ryan said that President Obama has allowed Iran to get four years closer to building a nuclear weapon.
Mr Biden said that he is "quite confident" the administration could deal a serious blow to Iranian's nuclear ambitions as it was still "a good way away" from acquiring a nuclear weapon.
He added: "We will not allow the Iranians to get a nuclear weapon."
Unlike Mr Biden, Mr Ryan is not a foreign policy expert but stood his ground in territory that is more familiar to the veteran senator.
The two also argued over the poor state of the US economy, with Mr Biden saying Republicans must take responsibility for obstructing the economic recovery.
The slow economy has been the dominant issue of the US election, and Ryan is expected to make a detailed case against Mr Obama's fiscal and economic policies leading to a growing national debt.
In turn, the pressure was on for Mr Biden to go where the President did not in his own debate, which was considered lacklustre by many observers.
He quickly did so, citing Mr Romney's opposition to the administration's successful car industry bailout.
He noted that it was not surprising given the Republican's recent videotaped comment in which he was heard saying that 47% of Americans view themselves as victims who depend on the government and refuse to take responsibility for their lives.
The moderator then pointed out that it is the first time two vice presidential hopefuls were of the Catholic faith.
The vice presidential hopefuls said their Catholicism informs their public policy decisions, but they came down on different sides of the abortion debate.
Mr Biden said his Catholic faith taught that life begins at conception but that he would not impose that belief on people of other faiths.
Meanwhile Mr Ryan said he opposes abortion but that the policy of a Romney administration would include exceptions in cases of rape, incest or when the life of the mother is at stake.
Early poll results showed voters equally split between the two politicians and those who were left undecided by the bruising encounter.
:: The next debate between Mr Obama and Mr Romney will be held on October 16.