President Barack Obama and Republican challenger Mitt Romney have clashed over US military strength and how to deal with crises in the Middle East in a third and final debate, as polls showed them deadlocked two weeks before the November 6 election.
With one last chance for both men to appeal to millions of voters watching on television, Obama was the aggressor from the start in Monday's debate. He criticised Romney, the former Massachusetts governor, on his proposals on the Middle East, mocked his calls for more ships in the US military and said Romney wants to bring the United States back to a long-abandoned Cold War stance against countries such as Russia.
Romney seemed set on maintaining his gains in the polls by assuming a calm and confident demeanour, like a commander-in-chief. He often agreed with Obama's foreign policy on issues such as the Iranian nuclear programme and the withdrawal from Afghanistan, though the two men did disagree when the debate reached China, its final topic.
Obama had a biting response during a discussion of the military's budget and size, when Romney said he would increase the number of ships built by the US navy. He said the US should typically have 300 and only had 285, its smallest size since 1917.
"Governor, we also have fewer horses and bayonets," said Obama.
Obama also said the Republican presidential candidate, by once declaring Russia a "geopolitical foe" of the US, was seeking to turn back the clock.
"The Cold War has been over for 20 years," Obama said, turning to Romney as they sat at a table before moderator Bob
Schieffer. "When it comes to your foreign policy, you seem to want to import the foreign policies of the 1980s."
Romney, wanting to make no mistakes that could blunt his recent surge in the polls, said Obama's policies toward the
Middle East and North Africa were not stopping a resurgence of the threat from al-Qaeda and growing extremism in the region, from Mali to Egypt.
"Attacking me is not an agenda," said Romney. "Attacking me is not how we deal with the challenges of the Middle East."
The two candidates agreed that the United States should defend Israel if Iran attacked the key US ally in the Middle
East, but Romney said he would tighten sanctions pushed by Obama that are already strangling the Iranian economy.
The Republican, whose central theme throughout the campaign has been a promise to rebuild the weak US economy, repeatedly turned the discussion back to economic matters, saying US national security depended on a strong economy.
But Obama fired back that Romney's economic plan was based on tax cuts that had not had their desired effect in the past.
Romney would not be able to balance the budget and increase military spending with such a plan, he said.
"The math simply does not add up," he said.

'Backbone' on Russia
According to a CBS instant poll, which came out on Tuesday, 53 per cent of Americans thought Obama had won the debate, and only 23 per cent thought Romney had won.
On Russia, Romney criticised Obama for an open-microphone comment he made to then-Russian President Dmitry Medvedev that he would have more "flexibility" after America's election.
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Instead of showing Russian President Vladimir Putin more flexibility, Romney said, "I'll give him more backbone."
The two candidates were tied at 46 per cent each in the Reuters/Ipsos online daily tracking poll. Other surveys show a similar picture.
Obama came to Boca Raton with the advantage of having led US national security and foreign affairs since 2009. He gets credit for ending the Iraq war and the killing of al-Qaeda leader Osama bin Laden in 2011.
But Romney had many opportunities to steer the conversation back toward the weak U.S. economy, a topic on which voters see him as more credible.
Alan Fisher, reporting from Boca Raton ahead of the debate, said that foreign policy is a key issue for voters.
"The idea that Americans don't pay attention to foreign policy [has been] blown apart by another poll which says 92 per cent of them are interested or very interested in America's place in the world," he said.
"Both men know the importance of this and are willing to bank any advantage they can get this late in the campaign."