Israeli Prime Minister Benjamin Netanyahu shows an illustration as he describes his concerns over Iran's nuclear ambitions during an address to the United Nations General Assembly, Sept. 27, 2012. (AP Photo/Richard Drew)

Israeli Prime Minister Benjamin Netanyahu will address a joint meeting of Congress on March 3, focusing on the dangers of Iran's nuclear program and the threat he says it poses to his country. The planned speech is laden with controversy: the White House sees it as a deliberate attempt to undermine U.S. negotiations with Tehran; other critics believe it's a political stunt aimed to help Netanyahu at home ahead of Israeli elections later in March.

Speaking on the "Charlie Rose" show earlier this week, national security adviser Susan Rice said Netanyahu's gambit, backed by Republican leaders, "injected a degree of partisanship" into matters of foreign policy and was "destructive of the fabric of the relationship" between the United States and Israel.

Beyond the political rumblings and rancor, there's a lot at stake -- not least the prospect of American military action against Iran should diplomatic efforts hit a wall. The deadline for arriving at the framework of a deal with Iran comes at the end of March. Here's what you need to know about the disagreement between the Obama administration and the Israeli prime minister.

Israeli Prime Minister Benjamin Netanyahu arrived in Washington on March 1, ahead of his speech to Congress. By accepting an invitation from the Republican Party to address Congress, the Israeli leader infuriated the Obama administration. (Reuters)

Where they agree

Neither Obama nor Netanyahu want Iran to have the capacity to build nuclear weapons. Both their governments, as well as many others in the international community, doubt Tehran's long-standing claim that its nuclear program is intended for civilian energy purposes only.

In general, they want to restrict Iran's ability to enrich uranium to weapons-grade levels. They also want to ensure that the time it would take for Iran to build a nuclear bomb, should it choose to -- known as the "breakout" period -- is as long as possible, allowing the international community a big enough window to take decisive action before Tehran can develop an actual nuclear arsenal.

Where they disagree

But while they share these basic ground rules, points of difference immediately pop up. Netanyahu and Obama, who disagree about lots of things, have opposing views on what should result from diplomacy with Iran: the Israeli prime minister wants Tehran's capacity to produce high levels of enriched uranium, used to make a nuclear weapon, to be shut down; the White House is okay with Iran maintaining a limited capacity under a strict set of guidelines.

What Netanyahu wants

Netanyahu, backed by other dissenting voices in Washington, has taken a hard-line stance on Iran, insisting that "no deal is better than a bad deal" that would allow Tehran to still be able to manufacture a nuclear weapon. He wants congressional allies in Washington to stop an agreement, halting the negotiations so greater pressure can be exerted on Iran through other means, primarily sanctions.

"We have many reasons to worry about the agreement that is being formulated now," Netanyahu said at a gathering of his rightist Likud party this week. “The world powers committed themselves to preventing Iran from getting a nuclear bomb, but from the emerging accord it appears that they have given up on that commitment and have come to accept the idea of Iran -- gradually over the years -- developing the ability to make the fissile material needed for many nuclear bombs."

Netanyahu has signaled now that he wants Iran to have no ability whatsoever to enrich uranium and that it should remove all its centrifuges, the cylindrical devices that enable enrichment.

Here's a quick explanation of how they work: the vast majority of natural uranium ore comes at what's understood to be U-238, a reference to the three extra neutrons in the nuclei of its atoms. To create the sort of nuclear chain reaction that's needed in atomic bombs, you need to use atoms that are easier to break apart -- U-235.

A stockpile of purified or "enriched" uranium is created by whirling around uranium gas in centrifuges at very high speeds so that heavier U-238 atoms spin off. The Washington Post created this illustration of how a generic American centrifuge works:


In 2012, Netanyahu famously grandstanded at the U.N. General Assembly, holding aloft an image of a cartoon bomb. He drew a red line close to the top, warning that Iran was amassing too much uranium enriched at 20 percent -- the "second stage" of enrichment before arriving at fissile-grade material.

As a result of an interim deal hatched in November 2013, Iran has diluted its reserves of uranium enriched at 20 percent -- its stockpile of most dangerous nuclear material. Iran still has some 8,000 kilograms of low-enriched uranium that could be converted through its centrifuges into material that could form the core of a nuclear weapon. The time it would take to complete that process is a matter of debate, as is whether Tehran would even be willing to take the strategic risk of pursuing a weapon. But it is enough to raise Netanyahu's hackles.

What the White House wants

It's clear that a total dismantling of its capacity is a nonstarter for Iran, whose nuclear program is a source of pride and nationalism across the country's political spectrum. Iran is a signatory to the Non-Proliferation Treaty, and its nuclear facilities are already subject to a strict regime of international monitoring. Nuclear-armed nations such as India, Pakistan and, yes, Israel (whose bomb is an open secret) are not. Iranians can justifiably point to the double standard of the scrutiny heaped on their nuclear capabilities.

The Obama administration appears to want a deal that would put Iran's program in what some analysts have called "an iron box" -- setting strict and clear controls over the country's nuclear capabilities, including the size of its enriched-uranium stockpiles, while making its facilities subject to even tighter international inspections.

Leaked reports from the sidelines of the negotiations suggest the United States would be willing to allow Iran to maintain some 6,500 centrifuges. The Associated Press has reported that at least a decade-long clampdown on Iranian nuclear activities has been proposed, and would be loosened over time based on Tehran's cooperation.

What's at stake

The Iranian government led by President Hassan Rouhani wants to reach a compromise that would ease the burden of sanctions placed on the country's economy. Rapprochement with Iran after decades of enmity would be a significant foreign policy win for the Obama administration, whose relations with Saudi Arabia, Iran's regional nemesis, have soured in recent years.

That would not be a welcome development for Netanyahu, who views the Islamic Republic as an existential threat to Israel. Not all Israelis agree with this analysis, including, apparently, leading figures within Israel's intelligence agency, the Mossad, as well as Netanyahu's chief opponent in the elections, Isaac Herzog. In an interview with The Washington Post, Herzog said Iran was "a big threat," but refused to agree with the Israeli premier that it is an "existential" one.

Beyond the mechanics and specifics of any prospective deal, there's a wider gulf between the Obama administration and Netanyahu. The White House believes keeping Iran at the negotiating table is itself a safeguard against Iran developing a nuclear weapon. A new round of sanctions would make it much harder for Rouhani and his government to subdue their own hard-line critics at home who want to scupper a compromise with the United States.

At a hearing on Wednesday, Secretary of State John F. Kerry hailed the success of previous rounds of talks between Iran and negotiators from the five permanent member states of the U.N. Security Council and Germany (known as the P5+1 bloc). "Israel is safer today with the added time we have given and the stoppage of the advances in the nuclear program than they were before we got that agreement, which by the way the prime minister opposed," said Kerry.

Others point to what happened during the previous administration of President George W. Bush. Talks with Iran broke down after Bush lumped Tehran into the "axis of evil." After that collapse, the Islamic Republic went from zero installed centrifuges to some 6,000 by the end of Bush's tenure.

If diplomacy fails, the pressure for more overt military action against Iran will grow. Another war in the Middle East, while appealing to some hawks, could be far costlier than a situation where Iran has the theoretical ability -- but not the strategic interest -- to generate weapons-grade enriched uranium.

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