President Barack Obama accused Republican candidate Mitt Romney of being consistently wrong on foreign affairs as the two presidential rivals squared off in their third and final debate.

Obama criticised Romney's support for beginning the war in Iraq, for opposing his plans to withdraw troops from Iraq, for inconsistent stances on Afghanistan and for opposing nuclear treaties with Russia. "Every time you've offered an opinion you've been wrong," Obama said.

Romney defended his stances and told Obama that "attacking me is not an agenda" for stopping violence in the Middle East.

The debate on foreign affairs came as international issues have taken a higher profile in a race that has been dominated by economic issues.


Romney and fellow Republicans have criticised the Obama administration's response to a September attack on the US consulate in Benghazi, Libya, that killed the ambassador and three other Americans. But asked about the attack at the outset of the debate, Romney did not directly criticise Obama as sharply as he had in the past, calling for a comprehensive strategy to reduce violence in the region. "We can't kill our way out of this mess," he said.

Foreign policy is generally seen as Obama's strength. He gave the order leading to the killing of terrorist leader Osama bin Laden and fulfilled a promise to withdraw US troops from Iraq. Romney, a former Massachusetts governor and wealthy businessman, has little foreign affairs experience.

But Romney has recently been on the offensive on international issues and has trimmed Obama's advantage in foreign affairs. In addition to the Libya criticism, he has accused Obama of being weak in opposing Iran's nuclear program, failing to defend US economic interests in relations with China, and not doing enough to support US allies like Israel.

Still, it was Obama who began the debate by criticising Romney. After a lacklustre performance in the first debate, Obama appeared keen to go on the offensive Monday, just as he had in last week's debate. The debate performances have been judged at least as much by the general impressions of the candidates as by their specific proposals. With polls showing few voters ranking foreign affairs among their top concerns, the candidates were vying to leave the impression that they are strong leaders.

Obama was seen as having the advantage going into Mondays' foreign policy debate at Lynn University in Boca Raton, Florida. But that also meant that expectations were higher for the president - a precarious position for a candidate in a tight race.

An NBC News/Wall Street Journal poll released Sunday showed Obama and Romney tied, with both candidates backed by 47 per cent of likely voters nationwide.

Both candidates were looking to energize their supporters in the final weeks of the campaign and win over a dwindling number of undecided voters in key states. The election is a state-by-state contest and the outcome in a small number of states that are not predictably Democratic or Republican will determine the winner.

To that end, China has been the focus of much of the foreign policy discussion, with both candidates tying it to the loss of US manufacturing jobs a big issue in Ohio, an important industrial state. Romney says Obama has failed to stop China from stealing American intellectual property or from keeping its currency artificially low, hurting US businesses. He has pledged to declare Chinese a currency manipulator, which could lead to sanctions.


Obama has highlighted actions he has taken against China before international trade bodies. He accuses Romney of outsourcing US jobs to China when he ran the private equity firm Bain Capital.

But the biggest issue lately has been Libya. Republicans say the Obama administration didn't provide enough security at the consulate in Benghazi and misled Americans by playing down the likelihood it was a terrorist attack. They say this reflects the failure of US policy in the Middle East.

So far, though, Libya has been a tough issue for Romney. A statement he issued immediately after the attack, before the death of the ambassador was known, was seen as ill-timed and opportunistic. And his attempt to confront Obama on Libya in the second debate backfired when the moderator supported Obama's claim that the president had called the killings an act of terror the day after the attacks. Obama's heated rejoinder calling Romney's comments offensive was one of the most widely played excerpts from the debate.

Monday's debate came as Iran's nuclear program is in the headlines, with reports that the Obama administration is holding open the possibility of one-on-one negotiations with Iran. Romney has pledged to be more forceful with Iran to prevent it from having the ability to develop nuclear weapons. Obama has pointed to his administration's role in implementing international sanctions that have hurt the Iranian economy. He has suggested that Romney could lead the US into another war like the one in Iraq.

The debate was being moderated by veteran newsman Bob Schieffer of CBS News.