An agreement would have been preferable, of course. But it’s not all bad news out of Vienna right now. The decision to extend until July the deadline for negotiations with Iran over the country’s nuclear program is, essentially, a step in the right direction. And making these talks a success has crucial implications far beyond Iran.

Iran’s nuclear program remains frozen during the negotiations, so Tehran cannot use the time to move closer to a bomb. If the talks had ended in complete failure, with both sides giving up and walking away from the negotiating table, Iran would no doubt restart its program, causing the United States and its allies to choose between military action and living with a nuclear-armed Iran. Either choice would have had devastating consequences, possibly marking a fatal blow to preventing the spread of nuclear weapons worldwide.

Nonproliferation efforts have been a central, bipartisan element in U.S. foreign policy since 1945. More than 180 countries have permanently relinquished their right to acquire nuclear weapons by ratifying the 1970 Nuclear Non-Proliferation Treaty (NPT) as “non-nuclear weapon states.” Only nine countries possess nuclear weapons. (Iran, if it were to acquire nuclear capabilities, would be the 10th.)

This small number stands in contrast to John F. Kennedy’s prediction that as many as 20 nations would be nuclear powers by 1964.

This small number stands in contrast to John F. Kennedy’s prediction that as many as 20 nations would be nuclear powers by 1964.

That’s the good news. But the United States and the world cannot be complacent. Two major problems seriously threaten to reverse past successes.

First, a major threat to nonproliferation comes from Russia. To compensate for its weakness in conventional military capabilities, Russia has made its long-standing emphasis on nuclear weapons more visible in its military budget, military doctrine, and exercises, and in statements by its military leaders. Vladimir Putin recently noted that Russia was “strengthening our nuclear deterrence forces.” Combined with its greater belligerence toward former parts of the Soviet Union and its incursions into Georgia and Ukraine, these nuclear threats have caused some defense officials in NATO member countries to worry about the credibility of U.S. security guarantees. In response, some NATO officials and private experts are urging the alliance to re-emphasize the role of nuclear weapons in its own defense plans and even to make the U.S. nuclear presence in Europe more prominent. Such renewed emphasis on the possibility of nuclear war might lead to further proliferation in Europe. And even a technologically advanced non-nuclear-weapon state far from the European conflict, such as Brazil, might come to believe it’s essential to follow the precedent of nuclear renewal for its own security ends.

Second, and most important to maintaining the role of nonproliferation, are the ongoing negotiations with Iran. For years, Tehran has denied that it seeks to develop nuclear weapons, yet the scale of its efforts to enrich uranium, its construction of a heavy-water reactor that could produce weapons-grade plutonium, and secretive experiments at a military base that were probably investigating means of triggering a nuclear device gave lie to these claims. For years, the international community sought to coerce Iran into ending these programs through sabotage, threats of military action, and far-ranging economic sanctions.

After years of false starts and empty talks, serious negotiations to place limits on Iran’s nuclear infrastructure in exchange for a lifting of sanctions began one year ago. They will continue well into the next year, as both Tehran and the West work toward a final, comprehensive agreement that would give Iran the peaceful nuclear capabilities it wants while guaranteeing it does not develop nuclear weapons.

While negotiations cannot go on forever, taking the time necessary to conclude an agreement is a wise course.

While negotiations cannot go on forever, taking the time necessary to conclude an agreement is a wise course. As a condition of starting the negotiations, significant aspects of Iran’s capability to produce a bomb — including the enrichment of uranium beyond the 5 percent used in power reactors — have been halted. Iran’s stockpile of such materials was eliminated. For its part, Iran received relief from a narrow set of sanctions and was permitted access to some oil revenues that previously had been frozen.

Each side’s negotiators have been constrained by hard-liners in their capitals who essentially stated that the only acceptable agreement would be one that incorporated total capitulation by the other side. That is a fantasy. Today’s announcement that negotiators settled on an extension to seek more time for a comprehensive deal will provide more time for domestic opponents to attempt to scuttle the talks.

If the negotiations succeed by the July deadline, the agreement will be a huge reinforcement for nonproliferation. It will forestall a nuclear arms race in the Middle East and demonstrate that the world community is united in preventing the emergence of any additional nuclear powers. Russia’s cooperation in successful negotiations with Iran could open a door for an easing of tensions and renewal of U.S.-Russia arms control negotiations.

If negotiations ultimately fail, the NPT will be in mortal danger. Even if the United States carried out its threat to strike militarily to prevent Iran from acquiring nuclear weapons, eventually Iran would rebuild, united for the first time behind a nuclear weapons program. Regional foes, like Saudi Arabia, would likely try to follow suit. The world stands on the brink of the widespread proliferation of nuclear weapons. Continued negotiations are a smart move. A nuclear agreement with Iran cannot be permitted to fail.