The last round of P5+1-Iran talks saw some high drama. On the second day, strong hints of a pending deal were bolstered by reports that the foreign ministers of the P5+1 were making their way to Geneva. But then, as quickly as expectations had risen, they rapidly began to dissipate, and the talks finally ended without a deal. The details of the P5+1 draft proposal are being kept under wraps, but clearly the French foreign minister introduced some crucial input to the text when he arrived in Geneva – regarding the facility at Arak, and the question of Iran’s right to enrich uranium on its soil. Faced with the altered proposal, the Iranians said they needed more time.

For years, those who have negotiated on behalf of the international community with Iran on the nuclear issue have suffered a debilitating weakness at the table due to their dependence on a negotiated settlement in order to achieve their goal of stopping Iran. All the while, Iran itself was never similarly tied to a negotiated deal, and could move unilaterally to its goal. For a long time this enabled Iran to use negotiations tactically in order to play for time, while simultaneously pushing forward its nuclear program.

For the first time, this situation is changing. The latest talks underscore that the impact of biting sanctions has made Iran also dependent on a negotiated settlement. It cannot get desperately needed sanctions relief without cooperating with the international community, a fact which should strengthen the hand of the P5+1 negotiators.

In the last round there were some indications that these states were indeed assuming the lead. For example, discussion focused on a P5+1 proposal, rather than Zarif’s PowerPoint presentation from mid-October. And once France’s reservations were incorporated into the P5+1 draft, they were quickly approved by all six parties, leaving no internal divisions for Iran to exploit.

So why is the Obama administration adamantly opposing further pressure on Iran? Kerry insists that if new sanctions are passed by Congress they would be viewed as bad faith by the Iranians, destroy the prospect of getting an agreement, and could even lead to military confrontation, presumably by pushing Iran to make a dash to the bomb.

These concerns are an exaggeration. Similar fears were raised before the biting 2012 sanctions were put in place, but they did not push Iran to exit the Treaty on the Non-Proliferation of Nuclear Weapons; rather, the pressure brought Iran back to the table, in line with its rational cost-benefit approach on the nuclear front. Indeed, the most likely result of further pressure would be Iran’s realization that it is not only dependent on the P5+1 for the relief it seeks, but that the pressure card will continue to be played. This would actually enhance the ability of the P5+1 to get the deal they want. Moreover, in the highly unlikely event that Iran were to react by rushing to the bomb, the regime would expose itself as having lied and cheated all along. Iran knows that this could trigger military action, in line with declared U.S. policy.

Clearly the United States greatly fears being put in a position where it would have no choice but to strike Iran militarily, but giving voice to this fear unfortunately risks weakening its hand, just at the time when it has finally become stronger. The United States is also concerned, as Kerry noted, that additional sanctions could wind up setting the United States back in dialogue that is has taken 30 years to achieve. But American concerns about squandering the long-term prospect of a changed bilateral U.S.-Iranian relationship should not interfere with the immediate focus on the nuclear file.

Iran is currently looking for a deal that will allow it to regain economic viability, while not giving up its ability to move toward a military nuclear capability. The original clause on Arak – that would have prevented Iran from commissioning the facility for six months, but would have allowed for continued construction work – is Iran’s tactic in a nutshell. To make “concessions” that are not concessions at all, because Iran was not on track to commission the facility in the next six months, but certainly wanted to be able to continue construction work so that it would be ready to do so later in 2014. And in return, to get sanctions lifted.

The only chance the P5+1 have to get the nuclear deal they want is by keeping Iran dependent on a negotiated deal for the sanctions relief they desperately need. It’s the last chance for a good deal, and the P5+1 should not surrender any of the leverage they have worked so hard to gain, before getting the results they seek. These states are today collectively much stronger than they might realize; it would be a grave mistake to succumb to unrealistic fears when steadfast determination is the order of the day.

Dr. Emily B. Landau is a Senior Research Associate at the Institute for National Security Studies (INSS). She is the author of "Decade of Diplomacy: Negotiations with Iran and North Korea and the Future of Nuclear Nonproliferation" (2012).