As President Barack Obama pushes to reach a nuclear deal with Iran by a Tuesday deadline, a small army of critics � from congressional Republicans to Israeli leaders to the Saudi royal family � is ready to pounce on any weaknesses to persuade Congress and the global community to turn against the pact.

�They are about to make a mistake for the ages,� Republican Sen. Lindsey Graham said last week.

Negotiators, critics, and outside experts will be closely watching six key areas of concern. The success or failure of Obama�s signature foreign policy initiative could hinge on how the final agreement addresses them.

Secretary of State John Kerry and negotiators from five other countries � France, Germany, Britain, China and Russia � are in Switzerland this weekend trying to reach a framework agreement by March 31 that would set the basic outlines of a much longer-term deal. The main goal is to ensure that Iran can�t develop a nuclear weapon faster than the outside world could stop it.

Such a framework would leave technical details to be nailed down before June 30. That�s is the only truly binding deadline on negotiators, because it is the expiration date for the current interim agreement that has capped Iran�s nuclear program in exchange for limited sanctions relief. Negotiators see March 31 as a political deadline established mainly so the Obama administration can show evidence of progress to impatient members of Congress.

If there�s no deal by March 31, there�s no practical reason the United States and its partners couldn�t keep negotiating. In practice, the real deadline of concern for the Obama White House is April 13, when the Senate is scheduled to return from its Easter recess � and will likely take up legislation cracking down on Iran if a framework is not in hand.

These are six of the core issues that any agreement in the coming days will need to address, and which both supporters and critics will be scrutinizing to see who got the better of the deal:

Setting the clock:�U.S. officials say their guiding star is to make Iran unable to acquire a nuclear bomb in less than one year. That�s enough time, the thinking goes, for the international community to detect any Iranian move to build a weapon and to respond with economic sanctions and possible military action. Some think Iran may now have a �breakout time,� as the experts call it, of as little as 3-6 months.

But critics of the deal, including Israeli Prime Minister Benjamin Netanyahu, think one year isn�t long enough. Any deal that produces a longer breakout time � of, say, 18 months � would be much easier for Obama to sell at home and abroad. But few observers expect that to happen.

And not everyone is sure to agree on the breakout time established by the provisions of a deal, which depends in part on complex technical calculations. When he spoke to Congress in early March, Netanyahu hinted that Israeli nuclear experts believe the deal would leave Iran less than one year away from developing a bomb.

Centrifuges:�Iran currently possesses about 20,000 centrifuges, which spin uranium at extremely high speeds to increase its purity � potentially high enough to make a nuclear bomb � but operates only 10,000 of them. When the nuclear talks first began in late 2013, Obama officials spoke of letting Iran run a couple of thousand centrifuges. Netanyahu says the number should be zero. According to recent reports, the U.S. is now offering to let Iran to operate around 6,500 centrifuges.

The centrifuge number is of limited value in isolation because there are so many other factors behind a nuclear deal. �Centrifuges are just one factor in the equation,� writes Joe Cirincione, president of Ploughshares Fund and a supporter of the nuclear talks. But news headlines and critics are likely to focus it because it is the simplest metric in the talks. Any figure below around 6,000 will be seen as a win for Obama; any figure above 7,000 as a concession to Iran.

Deal-watchers will also be looking closely to see how much research and development Iran is allowed to conduct into more advanced and efficient centrifuge designs, which could turbocharge its nuclear program in future years.

Nuclear material:�A nuclear deal will almost certainly limit the level to which Iran can enrich its uranium � allowing Iran to produce uranium potent enough to fuel a nuclear reactor, but not a bomb. (Think of whipping cream: The uranium is the cream and the centrifuges are the whisks. Iran will in effect be forced to stop whipping before the cream is fluffy.)

Iran will also likely be required to ship much of its nuclear material out of the country, probably to Russia, so that it can�t be diverted to a potential bomb. Any material it does keep will likely be limited to an enrichment level of 5 percent � well below the 90 percent enrichment level required to achieve a nuclear blast.

Coming clean:�The International Atomic Energy Agency says that Iran has refused to answer several questions about its alleged past research into nuclear weapons design. Iran denies that it ever conducted that research, but Western officials and the IAEA are dubious. A key question is whether a deal would require Iran to answer all of the IAEA�s questions immediately. Many Republicans and some Democrats in Congress insist that it must.

Skeptics will also be watching closely to see what degree of monitoring and inspection Iran will be forced to accept to ensure that it doesn�t cheat on any deal. �Iran will need to allow mechanisms to ensure that any further military nuclear related work would be detected on short order,� David Albright, president of the Institute for Science and International Security, told the House Foreign Affairs Committee in November. �Without these limitations on Iran�s nuclear programs and expanded verification conditions, a long-term deal will likely fail or exacerbate the threat from Iran.�

The more information Iran provides about its past military research, and the more transparent it is about its future activities, the more it will reassure wavering U.S. allies and members of Congress.

Sunset time:�A central question is how long any nuclear deal will last. Obama administration officials have set one decade as the minimum duration, down from the 20 years some floated early in the talks. Critics say that�s not enough time. French officials have been pushing for a 15-year deal, while Netanyahu says there should be no expiration date at all � the Israeli leader wants Iran freed from nuclear limits only when its theocratic regime stops threatening Israel and other countries in the region.

�We can insist that restrictions on Iran�s nuclear program not be lifted for as long as Iran continues its aggression in the region and in the world,� Netanyahu said in his March 3 address to Congress. That�s not going to happen. But a sunset date of longer than a decade would be a win for Obama, making a deal easier to defend.

Sanctions:�How many sanctions are lifted, and how quickly, will be a key measure of any deal. Iran came to the bargaining table in 2013 only after its economy had been crushed by harsh U.S. and United Nations sanctions. Iran has called for all sanctions to be lifted immediately. The United States insists upon a much slower pace, with most sanctions removed over time as Iran shows it�s honoring a deal.

The reality will be in the middle. But the longer sanctions endure, and the more requirements for their removal, the more palatable the deal will be to critics. And if reports are accurate that Iran has been promised immediate relief from United Nations sanctions, Congress is likely to fight back hard. Graham has called for cutting off U.S. funding to the United Nations if that happens. And GOP Sen. Ted Cruz told CNN that it �dramatically increases the likelihood that a new president in 2017 will face no other choice but launching military strikes against Iran to stop them from acquiring nuclear weapons.�

By Politico