Over the last three years, the United States has withdrawn from two longstanding arms control agreements with Russia and may withdraw from a third. These treaties were pivotal to reducing the chances of nuclear confrontation and ending them now is dangerous.

In withdrawing from the Intermediate-Range Nuclear Forces Treaty and the Open Skies Treaty, the president suggested he could craft better agreements from scratch. So far there is no evidence he has done so.

And now our last-remaining bilateral nuclear arms control treaty with Russia – New START – is at risk.

This start-from-scratch approach fails to take into consideration just how difficult it is to reach agreement on these treaties. Regarding New START, the far wiser course is to extend its provisions for five years and use that time to make any updates that may be needed.

Extending New START would cap Russia’s current strategic forces until at least 2026, offering greater predictability and transparency as we begin to replace our own aging nuclear weapons systems.

It would also allow us to continue the extensive and effective verification regime that allows us to monitor Russia’s adherence to the treaty’s terms and provides unique and valuable intelligence on the size, capabilities, location, and operation of Russia’s strategic forces.

An extension of New START would also provide us the time and space to negotiate a follow-on arms control accord with Russia, China, and other nuclear powers. Specifically, with limits on strategic forces remaining in effect through 2026, the United States and Russia would have the opportunity to pursue measures for the limitation and reduction of nuclear capabilities not covered under New START, such as hypersonic weapons and non-deployed nuclear warheads.

On the other hand, allowing New START to expire in February would likely represent the end of strategic arms control as we know it. It would lead to an expensive investment by the United States and Russia to expand and modernize our nuclear forces, which in turn could easily lead to additional nuclear spending by other nations – something clearly not in our interest.

Losing New START would also present greater uncertainties about Russia’s present and future nuclear plans and capabilities, leading to concerns about the adequacy of our deterrent posture and recurrent nuclear fears and crises similar to those we experienced during the Cold War, like the Cuban Missile Crisis.

Historically, the United States has built on the success of arms control agreements to craft new, stronger treaties.

Open Skies was first mentioned as a concept by President Dwight Eisenhower in the 1950s. It took decades to gain acceptance as an idea and to negotiate the terms before finally taking effect in 2002.

New START itself built on the successes of START I, a concept born during the Reagan administration but not signed until nearly 10 years later. Even then, New START took eight rounds of bilateral talks with Russia before an agreement was reached and the treaty implemented in 2011.

The point is that international arms agreements rarely move swiftly. They involve years of detailed discussions by career negotiators and most often are the result of building on a foundation of an expiring agreement.

I know because, as a co-chair of the Senate’s National Security Working Group, I observed New START negotiations between the U.S. and Russian teams. It is enormously complex and difficult. Jettisoning New START to go back to the drawing board is, at best, an enormous risk.

What’s more, our credibility is damaged every time we cancel an agreement. What assurances do other countries such as Russia, North Korea or China have that we will commit to a treaty if we repeatedly cancel agreements before their terms expire?

The core concepts that serve as the foundation of New START – reinforcing mutual deterrence, inhibiting costly and dangerous arms races, and allowing for extensive verification measures that reduce the opacity of competition – still hold true. And the threat environment that we currently face would become even more complex and challenging without New START.

Fortunately, New START contains a provision that allows for a five-year extension by simple executive agreement. President Vladimir Putin has already made clear that Russia would agree to this, and I call on President Donald Trump to do the same.

There’s no question that our existing arms control treaties with Russia need to be updated and improved upon. But that’s best accomplished by building on what we already have. The perfect cannot become the enemy of the good when so much is at stake. President Trump should extend New START immediately.

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