Of all the details about the historic deal limiting Iran’s nuclear program, announced early this morning in Geneva, the most salient one may be its scope: It is intended to last for only six months. The focus should now turn to forging a permanent agreement to prevent Iran from ever obtaining nuclear weapons.

Increased sanctions pressure (from the U.S. and its allies) and rapid progress in developing a nuclear program (in Iran) brought Iran and much of the rest of the world to a fork in the road: One path, increased sanctions, would lead to eventual airstrikes, a cycle of retaliation and a delay in Iran’s nuclear progress. The second path, a diplomatic agreement, would result in limiting and monitoring Iran’s program. The latter was easily the better choice, and it appears to have been made possible by some secret backroom diplomacy for which the Obama administration deserves credit.

Israeli leaders were nevertheless furious at the terms of the deal, with Prime Minister Benjamin Netanyahu describing it as a “historic mistake.” Israel has unique cause for concern regarding the prospect of a nuclear-armed Iran. It is worth remembering, however, that today’s deal is just an interim step, aimed at creating the time and space necessary to strike a permanent settlement.

Iran agreed to take the essential steps required to freeze its progress, which include halting enrichment of uranium to 20 percent, just a short leap from weapons grade, and converting its stockpile of the fuel to less dangerous forms. Iran also agreed to accept more intrusive inspections -- in some cases daily -- by the International Atomic Energy Agency. In exchange, the so-called P5+1 -– China, France, Germany, Russia, the U.K. and the U.S –- have relaxed about $7 billion worth of the $100 billion worth of sanctions in place.

Netanyahu is correct that today’s agreement makes it clear that any final agreement will leave Iran with an enrichment capacity, albeit limited and monitored. This is a departure from United Nations Security Council resolutions in place since 2006, and the zero-enrichment demands the U.S. and its European allies have been making for the last 10 years. That strategy, however, failed. Today’s tacit acceptance that Iran will be allowed to go on enriching uranium up to 5 percent merely recognizes this failure.

A permanent settlement needs to meet the legitimate concerns of Israel, Saudi Arabia and others in the region -- not to mention the repeated pledges of President Barack Obama that Iran never become a nuclear armed state.

It is a difficult goal, made more so by Iran’s repeated violations of its past promises. Nevertheless, the U.S. Congress would only make it worse by trying to force through new sanctions during the period of the talks -– something the interim deal says must not happen.

Critics of the interim agreement are right that Iran may use the negotiations to run out the clock, gradually wearing down sanctions but leaving Iran with the freedom to develop nuclear arms. The best way to prevent this is to make clear to Iran’s leaders that failure so late in the game would mean military action, while success could lead to other deals Iran craves, on trade and regional security.

The real test of Iran’s intentions comes now, not just in whether it implements the terms of the interim deal but also in how aggressively it pursues a final agreement. That’s what supporters and critics of this first-step agreement should be watching.

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