Barack Obama and Republican rival Mitt Romney will tangle over foreign policy in their final presidential debate, with both candidates still looking for a breakout moment in a deadlocked White House campaign two weeks before Election Day.
Polls show Obama with a small advantage in voter perceptions about which candidate is best prepared to handle US foreign policy in chaotic world.
Romney will do his best in the 90-minute debate in Florida to minimise the president's accomplishments and win the support of the small slice of undecided voters among the millions of Americans who will be watching.
Both candidates usually campaign on domestic issues, but the former Massachusetts governor has been hitting Obama hard on the administration's changing explanations of what happened in last month's attack on the US Consulate in Benghazi, Libya, where militants killed four Americans, including Ambassador Chris Stevens.
The Syria violence, Iran-Israel tensions, China, terrorism and the war winding down in Afghanistan were also expected to come up in Monday's debate.
Moderator Bob Schieffer of CBS News has picked five topics, devoting the most time to the Middle East and terrorism. Other subjects are America's role in the world, Afghanistan and Pakistan, Israel and Iran, and the rise of China.
Obama and Romney don't differ as sharply on foreign policy issues as they do on domestic issues such as the economy. One difference is their personal relationships with Israeli Prime Minister Benjamin Netanyahu, who is a friend and former colleague of Romney but has a chilly stance with Obama.
As the November 6 vote approaches, 41 of the 50 US states are essentially decided, and the candidates are fighting over the remaining nine battleground states, including the critical Ohio and Florida.
'It really now comes down to that small segment of undecided voters,' deputy Obama campaign manager Stephanie Cutter told NBC on Monday. 'We feel pretty good about where we are.'
The battleground states assume outsized importance because the presidency is decided in state-by-state contests, not by a national popular vote. The system can lead to a candidate winning the popular vote but losing the presidency, as former vice-president Al Gore did in 2000.
A new NBC News/Wall Street Journal poll released on Sunday showed Obama and Romney tied, with both candidates backed by 47 per cent of likely voters nationwide.
The poll was conducted after the second presidential debate last Tuesday that Obama was seen as winning after a poor performance in the first debate on October 3. In the last such poll before the presidential debates began, the president held a three-point lead over Romney, 49 per cent to 46 per cent.