US running mates clash in debate
Key moments from the debate between the vice-presidential candidates, Democrat Joe Biden and Republican Paul Ryan.
Mr Ryan said the Obama administration's foreign policy was "unravelling", citing last month's attack on the US consulate in Benghazi in which the US ambassador to Libya was killed.
"When we show that we're cutting on our defence, it makes us more weak," he said, adding that "our adversaries are much more willing to test us".
Mr Biden countered by describing Mr Ryan's claims as a "bunch of malarkey", blaming the Republicans for cutting the embassy security budget by $300m below what the White House asked for.
The vice-president also dismissed the suggestion that the Obama administration was weak, saying the president "has repaired our alliances so that the rest of the world can follow us again".
Mr Ryan said that "a nuclear-armed Iran which triggers a nuclear arms race in the Middle East" was the worst possible option.
"We can't live with that," he stressed, accusing the Obama camp of having "no credibility on this issue".
Mr Biden began by saying that "war should absolutely be the last resort", adding that America should continue with "crippling sanctions" against Iran that were working.
"This president does not bluff," he said.
Mr Ryan said a 20% tax cut proposed by Republicans would work if loopholes and deductions available to high earners were closed.
He also said the Romney team would work hard to try to secure bipartisan agreement on the issue.
Mr Biden parried by saying the proposal was "not mathematically possible".
And he stressed that the Republican plan would hurt ordinary Americans.
Mr Ryan accused President Obama of trying ineffectually to resolve the Syrian conflict through the UN and also relying on Russia, a key backer of Damascus.
"It's been over a year, the man (Syrian President Bashar al-Assad) has slaughtered tens of thousands of his own people," he said.
In response, Mr Biden responded by asking what Republicans would do differently.
He said that for months humanitarian and "other aid" had been going to "free forces" in Syria, and America's allies - both in the West and Middle East - were on "the same page" on the issue.
As Roman Catholics, both Mr Biden and Mr Ryan said they followed the Catholic Church's guidance on the issue, stressing that "life begins at conception".
However, Mr Biden added that he refused "to impose that [view] on others", arguing that it was each individual woman's right to choose.
Mr Ryan criticised the administration over healthcare policies which he claimed force religious institutions to provide services that clash with their beliefs.
Romney's 47% remark
Perhaps inevitably, Mitt Romney's unfortunate campaign remark that the 47% of Americans who pay no income tax are Obama supporters was raised. Mr Ryan suggested that it was a Joe Biden-style gaffe.
"Sometimes the words don't come out of mouth the right way," he joked.
Mr Biden is known for the occasional blunder during his public speeches. But his quick-fire reply was: "I always say what I mean... And so does Mitt Romney."
The vice-president also urged the Republicans to "get out of the way" to make tax cuts for the middle class permanent.