For half a century, at Semipalatinsk and at the Nevada Test site, nuclear weapon explosives tests dotted the landscape and shook the Earth. All told, 928 tests were conducted at the grounds of the Nevada Test Site and 456 at Semipalatinsk, and many more elsewhere.

Rival scientists from the U.S. and Soviet nuclear weapons laboratories used these testing proving grounds, including the one just 800 kilometers from here, to prove and showcase their powerful new weapons designs. Every month, new holes for nuclear weapons were burrowed into sides of mountains or lowered by “racks” deep in the Earth, all in support a Cold War arms race that spanned decades.

Steadily, we have made progress in reducing nuclear dangers since the Cuban Missile Crisis when the United States and former Soviet Union were brought to the nuclear brink. The Limited Test Ban Treaty (LTBT) of 1963 made it so that the skies over the United States, Kazakhstan, and the rest of the globe, would no longer be clouded by harmful radiation from atmospheric nuclear weapons tests. The end of the Cold War was soon followed by a moratorium on all U.S. and Russia nuclear explosives testing; today only one state – North Korea – continues nuclear testing, despite overwhelming international pressure and condemnation. All of these changes occurred as Kazakhstan won its independence a quarter century ago, soon emerging as a global nonproliferation leader, a distinction that Secretary Kerry was quick to note in his visit to Astana last fall.

Not only did Kazakhstan foreswear nuclear weapons inherited from the Soviet Union by joining the Nuclear Non-Proliferation Treaty (NPT) as a newly independent non-nuclear weapon state, it also embraced nuclear security initiatives to foreclose the possibility of terrorists acquiring left-over fissile material from the former test site. Nuclear weapon scientists from the United States and Russia, once rivals, teamed with the government of Kazakhstan in a trilateral effort to seal off tunnels at the Semipalatinsk testing site and secure fissile material that posed a risk to health and to international security.

The United States, in concert with allies and partners like Kazakhstan, has achieved remarkable progress on a number of fronts since the end of the Cold War, including the elimination of much of the U.S. and former Soviet nuclear stockpiles. Progress has continued since President Obama’s landmark 2009 speech in Prague: we have reduced our deployed stockpiles and launchers through the New START Treaty, diminished the role of nuclear weapons in our security strategy, strengthened the tools and structures to prevent nuclear terrorism, and secured the Iran deal to block all of Iran’s pathways to a nuclear weapon.

President Obama has proposed to make even further progress. In Berlin in 2013, he unveiled a proposal to seek further reductions up to one-third below those levels in the New START Treaty in a manner that takes stock of what capabilities would be required to maintain a strong and credible strategic deterrent. As we have continued to make clear, progress in that direction requires a willing partner and a strategic environment conducive to further reductions.

We are also working actively to begin negotiations on a treaty that would halt the production of fissile material for use in nuclear weapons. Such a treaty, when combined with an in-force Comprehensive Nuclear-Test-Ban Treaty, would be fundamental to stopping arms races in their tracks and constitutes an essential step that can lay the foundation towards a global reduction in the number of nuclear weapons. Pending entry into force of the CTBT, we call on all states to maintain the moratoria on nuclear explosive tests. Sustaining these moratoria is in the national security interest of the United States, as well as that of the entire world.

The United States is engaging Members of the UN Security Council on a resolution that would emphasize the importance of maintaining these moratoria and would build support for the completion of the Treaty’s verification regime, based on International Monitoring System.

The United States is also engaged in a serious effort to inform the public and Members of Congress of why bringing the CTBT into force and improvements in its verification architecture are in our own national security. And we applaud Kazakhstan’s continued leadership role in promoting the CTBT’s entry into force, which is the only way to make permanent the benefits of the Treaty.

Even as the United States builds upon decades of pragmatic steps to reduce the role and number of its nuclear weapons, a group of countries are pursuing a polarizing and unverifiable nuclear weapons ban treaty that could actually end up harming the proven, practical, and inclusive efforts that have achieved tangible results on disarmament and will continue to do so. We know that nuclear disarmament can only be achieved through an approach that takes into account the views and the security interests of all states.

That is why we reject the final report from the Open Ended Working Group on nuclear disarmament (OEWG), which recently completed its work. The United States calls on all states to reject unrealistic efforts to ban nuclear weapons. The OEWG final report and efforts to institute a legal ban on nuclear weapons fail to take account of the international security environment and will neither lead to the elimination of nuclear weapons nor uphold the principle of undiminished security for all.

So, together let us reject division and instead agree that we share a common goal and recommit to the roadmap we are on, one that has proven results. Together we can make true the hope expressed by President Obama in Hiroshima: to refocus “the wonders of science on improving life, rather than destroying it.”