“There is only one sane policy, for your country and mine, to preserve our civilization in the modern age: A nuclear war cannot be won and must never be fought.” These were President Reagan’s words in 1984. They paved the way for nuclear arms reduction for years to come. This is one of the greatest diplomatic achievements in the last 40 years.

Today, that achievement is at risk. Russia, a permanent member of the UN Security Council is violating the principles of the United Nations Charter. Russia’s invasion of Ukraine, Vladimir Putin, and his sycophants veiled threats to use nuclear weapons, and his hold on Ukraine’s nuclear power plants threaten international peace and security. Russia’s actions are threatening a possible nuclear and radiological catastrophe in Europe.

The United States and the UN Security Council must respond to Russia’s behavior. In addition to the use of sanctions against Russia, a diplomatic strategy is necessary.

First, the United States should open backchannel talks with Russia, if they haven’t already done so. The dialogue behind closed doors should address Russia’s non-collaboration in global nuclear security, and work to clarify Putin’s statements and rationale. It should outline requirements for Russia to end its nuclear threats and rhetoric and cease shelling in or near Ukrainian nuclear power plants.

Second, the United States and its allies should consider a new package of sanctions on Russia’s energy exports and implement price caps in response to Russia’s nuclear threats. The U.S. can mitigate Russia’s energy cuts to Europe by supplying oil and natural gas to Europe, and further develop clean energy technologies. This strategy will discourage rogue states from future geopolitical advancement via nuclear threats. It will help Europe to survive in winter, allow it to transition smoother to clean energy in the long run and constrain Putin’s energy leverage aimed at disrupting such change.

Third, the United States needs to do all in its power to make sure that there is no use of nuclear weapons. It should make clear to Russia that there would be a powerful U.S. response if Russia conducts such an attack. The United States should reserve an option to launch a cyberattack to disable Russia’s military and nuclear systems and follow up with exercises demonstrating capabilities in Ukraine. The U.S. should make clear, however, that it will not cross the nuclear threshold.

There is concern as to whether such a diplomatic dialogue would be successful. Russia is like the Soviet Union of the past. It has brought the world closer to nuclear catastrophe with its nuclear brinkmanship. Yet, the strength of a diplomatic strategy is maintaining the lines of communication to better assess Russia’s rationale and thinking in order to be prepared and possibly avoid miscalculations by either Russia or the United States.

Additionally, Russia might demand an end to U.S. sanctions and military and financial aid to Ukraine. Time has shown that the U.S. and Western Europe are successful when they stand united in condemning Russia’s misconduct. The U.S. and its European allies should continue their support for Ukraine and their sanctions against Russia to preserve Western unity and cohesion in response to Russia’s aggression. The U.S. should make clear that the extent of aid to Ukraine and sanctions on Russia will depend on Russia’s behavior.

Diplomatic dialogue combined with economic sanctions have the greatest chance of keeping the door open to ending Russia’s war with Ukraine. It would likely prevent a possible nuclear and radiological catastrophe, and future nuclear proliferation.

The United States and the Western allies must act now to initiate that dialogue and remind Russia that nuclear brinkmanship is immoral and that it should join the West in supporting humanity and civilization. Reagan’s words and actions showed us how a strong U.S. commitment to diplomacy achieved global peace and the reduction of nuclear weapons. It was proven once. It is still effective now.