WASHINGTON (AP) — Barack Obama and Republican rival Mitt Romney confront each other on foreign policy Monday night in a third and final presidential debate, a must-win televised face-off heading into the final two weeks of the deadlocked campaign for the White House.

Polls show Obama with an advantage in voter perceptions about which candidate would do best in foreign affairs, but Romney is expected to use the head-to-head meeting in Boca Raton, Florida, to whittle away the president’s edge. He has been hitting Obama hard on the administration’s uncertain explanations about what happened in last month’s attack on the US Consulate in Benghazi, Libya. Militants killed four Americans, including US Ambassador Chris Stevens.

Iran-Israel tensions, China, terrorism and the war in Afghanistan were all subjects expected to come up in the 90-minute debate moderated by CBS News’ Bob Schieffer.

Against the background of the debate, 41 of the 50 US states are essentially already decided, and the candidates now are fighting to win in the remaining nine battleground states, including critical Ohio and Florida.

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, as it did in former Vice President Al Gore’s defeat in 2000, lead to a candidate winning the popular vote but losing the presidency. George W. Bush eked out a victory in the electoral college after the US Supreme Court stopped the recount in Florida.

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

The poll was conducted entirely in the aftermath of the second presidential debate last Tuesday that Obama was perceived as winning following a poor performance in the first debate on Oct. 3. In the last such poll before the presidential debates began, the president held a narrow, three-point lead over Romney, 49 percent to 46 percent.

But among the wider pool of all registered voters in the latest survey, Obama is ahead of Romney by five points, 49 percent to 44 percent.

Looking at some of the most important demographic groups, Romney leads among men (53 percent to 43 percent), Obama is up with women (51 percent to 43 percent) and they are essentially tied among voters in the Midwest.

With early and absentee voting already under way in many swing states, including Ohio, North Carolina and Iowa, the tight poll results indicate that the race could be decided by which campaign is better able to lock in supporters and get them to the polls.

Monday’s debate represents the candidates’ last chance to directly confront one another before an audience of millions of Americans watching the televised face-off.

Obama spent the weekend with top aides preparing for the debate at Camp David, the presidential retreat in Maryland’s Catoctin mountains. Romney did his pre-debate work in Florida, continuing intensive preparations that have consumed large amounts of his time in recent weeks.

In addition to the continuing political tussle over what happened in Libya, reports flashed around Washington over the weekend about developments in the administration’s efforts to end Iran’s suspected drive to build a nuclear weapon. The White House denied a New York Times report that there was an agreement in principle for bilateral talks with Tehran after the election. White House National Security Council spokesman Tommy Vietor, however, said that the Obama administration had repeatedly expressed its willingness for such talks.

Romney on Sunday refused to say if he would be open to one-on-one talks with Iran if elected. He was asked about Iran while officiating a coin toss at a flag football game on a Florida beach between reporters and his senior campaign aides. Romney, who was taking a break from debate preparations, also declined to say how he was feeling about the Monday debate or the new poll showing a close race.

Iran’s economy is suffering mightily under a series of international sanctions aimed at convincing the Islamic Republic to stop uranium enrichment, a precursor to creating a nuclear weapon. Obama has said if diplomacy and sanctions fail, he was ready to use military action. So has Romney, although he has said US threats should be more robust.

Republicans accused Obama of leaking word of possible negotiations with Iran in pursuit of political gain. Democrats shot back, arguing that Romney and his party are the ones playing politics with national security.

Obama has ranked well with the public on his handling of international issues and in fighting terrorism, especially after the daring US raid that killed Osama bin Laden deep in Pakistan. But the administration’s response to the Libya attack and questions over levels of security at the Benghazi consulate have given Romney and his Republican allies an issue to question Obama’s foreign policy leadership.

Heading into the campaign’s final two weeks, the economy and other domestic issues remain the main focus of both candidates.

Romney has intensified criticism of Obama, claiming he has failed to tell Americans what he would do with a second four-year term. Obama is fighting back aggressively, insisting that Romney is hiding details of his much ballyhooed plan to cut federal income tax rates across the board. Obama says Romney can’t make all the tax cuts he has proposed without adding to the deficit or shifting more of the tax burden from the wealthy to the middle class.

Romney also has vowed to repeal the president’s health care reforms, but Obama says Romney has failed to say what he would do to replace the law which would provide health insurance to 30 million Americans who now have no coverage.

The Obama campaign has also stressed that it’s hard to predict what Romney might do as president, since he has changed his positions on many issues.

The president planned an extensive tour of battleground states after the debate, with events in Florida and Ohio on Tuesday, including a joint event with Vice President Joe Biden in Dayton, Ohio, before returning to the White House. Romney and running mate Paul Ryan planned to campaign Tuesday in Colorado.

On Wednesday, Obama was packing his schedule with around-the-clock campaigning in Davenport, Iowa; Denver; Los Angeles and Las Vegas, followed by events in Tampa, Florida; Richmond, Virginia; Chicago and Cleveland on Thursday.

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Copyright 2012 The Associated Press.