The stakes are huge -- for Iran, the United States, Israel, the wider Middle East and beyond.

Will the negotiations result in a deal that sets relations between Iran and the West on a more stable path? Or will they end in disarray and disappointment, bringing fears of confrontation down the road?

Here are answers to some of the key questions about this pivotal point.

1. What do world powers want?

They aim to restrict Iran's nuclear program to prevent Tehran from developing an atomic bomb. The countries negotiating with Iran are the United States, the United Kingdom, France, Russia, China and Germany.

2. What does Iran want?

Iran is desperate to get rid of the sanctions that have stifled its economy for years. But it also wants to keep hold of as much as it can of its nuclear program, which it insists is for peaceful purposes.

3. What's the deadline?

After years of tortuous negotiations, the parties had set a deadline of the end of Tuesday in Lausanne, Switzerland, to reach a framework agreement -- a political understanding on the main principles of a deal. But the talks have now stretched well past that self-imposed limit.

4. What happens if a deal is reached?

Negotiators move on to the next phase. They'll have until the end of June to thrash out all the technical details, building on the framework to make it a comprehensive deal. That's no formality: Some of the trickiest issues could get left for the final phase.

5. How will it play out around the globe?

Israel, which has voiced strong opposition to the emerging agreement, is likely to aggressively protest a deal. Other U.S. allies in the region, like Saudi Arabia, may also be unhappy. U.S. President Barack Obama will face opposition to the deal from Congress, which has threatened more sanctions against Iran. Hardliners in Iran are expected to attack the deal for being too restrictive.

6. So, will a deal survive the political fallout?

It's too early to say. Richard Haass, president of the Council on Foreign Relations, says he expects the bigger political battle over the deal to take place in the United States. "Iran is an authoritarian system. At the end of the day, if the Supreme Leader wants this deal, he gets it," Haass told CNN. "President Obama, whatever his critics think, is not a supreme leader. He's going to have much more trouble selling it here."

7. What if there's no deal?

Things could get even more hairy. You can expect more sanctions on Iran, which would continue on its path of nuclear development. That's likely to prompt other nations in the Middle East to pursue nuclear programs. In the United States and Israel, talk would resume about the possibility of bombing Iranian nuclear sites. "These are obviously wildly unattractive alternatives," Haass said. "We're not looking to have another war. We don't want to see a Middle East, as bad as it is, get even worse with nuclear weapons under multiple hands of control."

8. What kind of deal is expected to emerge?

World powers are seeking the outlines of an agreement they say would prevent Iran from obtaining a nuclear weapon for at least 15 years. In exchange, Iran would get relief from the damaging sanctions. But what exactly will be announced remains fuzzy. Officials have been vague about the format the framework deal might take, as well as how much of it will be made known to the public and international stakeholders.

9. What are the main sticking points in the talks?

Talks are believed to have gotten snagged on a number of key points. Chief among them are the pace at which the U.N. sanctions on Iran will be lifted and how much nuclear research and development Iran will be allowed to do while the deal is in effect. Tehran would like the sanctions removed as soon as a deal is signed, but Washington and other powers say the sanctions need to be lifted in phases and be able snap back into place if the Iranians fail to comply. Iran also wants to be allowed to develop more advanced centrifuges while the deal is in effect. U.S. and European officials worry that could enable Iran to quickly produce enough material for a nuclear weapon.

10. What are centrifuges?

Tube-shaped machines that use centrifugal force to turn natural uranium into highly enriched uranium, the key ingredient needed to make a nuclear bomb. Iran has about 18,000 centrifuges, 10,000 of which are still spinning today. Under a deal, the country would likely have to cut down the number of centrifuges it uses to about 6,000.

11. What about Iran's nuclear stockpile?

That's another unresolved issue -- what happens to Iran's existing stockpile of enriched uranium? The United States and its Western allies fear Iran could rush to enrich that uranium to levels high enough to make a nuclear bomb. One plan under discussion was for the stockpile to be shipped out of Iran, turned into material that works as fuel but not as a weapon and then sent back. An Iranian official said Sunday that Tehran wouldn't agree to its stocks being taken out of the country. U.S. officials denied suggestions Iran was backing off from a previous agreement on the issue. "This is a remaining issue that we have to resolve but hasn't, quite honestly, been one of the toughest ones," U.S. State Department spokeswoman Marie Harf said.

12. How will we know Iran is living up to its side of any deal?

The general view among nuclear experts and officials from various countries is that Iran would need to be subjected to a rigorous inspections regime to make sure that it sticks to the deal. "We are likely to get from this deal one of the most intrusive inspection regimes ever put in for any agreement of this type," said Joseph Cirincione, the president of Ploughshares Fund, a global peace and security foundation. "All of this would be supervised by international inspectors."

13. What if some nuclear sites are kept secret?

International inspectors have access to all Iran's declared nuclear facilities, but there's a big concern that Iran could also be advancing its nuclear ambitions at hidden sites. That's what's prompting calls for extremely intrusive inspections that would allow international monitors to travel throughout Iran and gain access to any facility. But that's unappealing to Iran, which already says it's being treated differently from other countries that have faced inspections. Western countries say Tehran deserves special treatment after having repeatedly attempted to cheat previous accords and hide nuclear facilities.

14. What if Iran doesn't honor the deal?

If world powers have their way, the sanctions would snap back into effect. Beyond that, it would depend on the nature of Iran's breach and what measures are in place for dealing with it. If the agreement unravels completely, the United States and its allies would be faced with difficult choices over what steps to take to curtail Iran's nuclear program. Calls for a military approach would make a comeback. There would, in theory, be some breathing space. World powers are aiming to make sure Iran would need at least a year to build a bomb, should it "break out" of the deal.

15. Why is Israel opposing a deal?

Israel sees Iran as an existential threat. Israeli Prime Minister Benjamin Netanyahu said over the weekend that the deal he believes is taking shape is "fulfilling our deepest fears and even worse." Israel says it has the most to lose if Iran, which refuses to recognize Israel's right to exist, develops a nuclear bomb. Tehran has supported armed groups that have engaged in direct conflict with Israel, like Hezbollah and Hamas. But Netanyahu's strong opposition has severely strained relations with the White House.

16. Who else is skeptical?

Saudi Arabia. It's a majority Sunni Muslim country. Iran is overwhelmingly Shiite Muslim. Saudi Arabia, like Israel, is troubled by Iran's growing clout in the Middle East. Analysts see the Saudis and Iranians as being engaged in a proxy war across the region, most recently in Yemen, where the Saudi military is carrying out airstrikes against Shiite rebels allied with Tehran. Saudi officials have expressed displeasure previously at the prospect of a deal between Iran and world powers.

17. How did Iran's nuclear program start?

The United States launched a nuclear program with Iran in 1957. Back then, the Shah ruled Iran and the two countries were still friends. With backing from the United States, Iran started developing its nuclear power program in the 1970s. But the United States pulled its support when the Shah was overthrown during the Islamic Revolution in 1979.

18. Is Iran the only nation with a nuclear program?

Eight nations are known to have nuclear weapons, including all the countries negotiating with Iran, with exception of Germany. Israel has always declined to confirm whether it has any, although the Federation of American Scientists estimates it has about 80 atomic weapons. It's unclear exactly what stage North Korea's nuclear weapons program has reached; the secretive East Asian nation has conducted three underground atomic tests.

19. Why have the other nations not faced as much scrutiny?

For nuclear-armed nations like India and Pakistan, no action was taken partly because they never signed the Treaty on the Non-Proliferation of Nuclear Weapons. "There was very little that the U.S. could've done to stop Pakistan," said Mark Hibbs, a nuclear policy expert at the Carnegie Endowment for International Peace. Iran, on the other hand, signed the treaty. And as a result, its program was put under the spotlight. In addition, the International Atomic Energy Agency had information suggesting Iran conducted activities it hasn't declared in the past.

20. Why is Iran's nuclear program considered such a threat?

Since the 1979 revolution, Western countries have worried that Iran could use its nuclear program to produce atomic weapons using highly enriched uranium. About a decade ago, international inspectors announced that they had found traces of highly enriched uranium at an Iranian plant in Natanz. Iran temporarily halted enrichment, but then resumed enriching again in 2006, insisting it was allowed under its agreement with the International Atomic Energy Agency. The prospect of an Iranian nuclear weapon stokes fears of a nuclear arms race across the already unstable Middle East. And then there's Tehran's longstanding antipathy toward Israel and the United States.

21. What would a military attempt to take out Iran's nuclear facilities look like?

It's uncertain how much of Iran's nuclear capability airstrikes would be able to take out. But the consequences would be dire. "People talk very cavalierly about these strikes. It's really appalling to me that this kind of discussion goes on," said Cirincione. "This is not a pinprick attack. This would be weeks of hundreds of U.S. sorties. This would be the beginning of a major war in the Middle East that would make the wars in Afghanistan and Iraq look like warm-up acts, and it would have regional consequences."