AT A time of growing mistrust with Russia, why needlessly make the situation more opaque? President Trump is reported to be on the verge of pulling the United States out of the Open Skies Treaty, a pact that went into force in 2002 and provides some transparency about military deployments on the ground. It has been particularly useful for monitoring the conflict in eastern Ukraine being fueled by Russia. Why suddenly put on blinders?

This treaty, which has 34 signatory nations, is not one of the weighty arms-control pacts such as the Anti-Ballistic Missile Treaty or the Intermediate-Range Nuclear Forces Treaty, both now dead. Rather, Open Skies is a useful confidence-building measure, allowing participants to carry out short-notice, unarmed overflights of other countries with airplanes containing sensors that detect and record military activity on the ground. The flights are governed by treaty rules, and data must be shared with the host country and can be made available to other signatories. While the United States also has impressive satellite monitoring ability, the Open Skies Treaty brings in countries that do not have such means.

The United States and Russia have had some differences over compliance with Open Skies, including about flights over Russia’s Kaliningrad enclave and the territories of Abkhazia and South Ossetia. But these disagreements hardly justify a pullout. Rather, Mr. Trump’s decision is reportedly at the urging of his former national security adviser John Bolton, who harbored a long-standing dislike of treaties that he considered overly restrictive on the United States. The decision to withdraw has not been announced but might be soon.

Mr. Trump should reconsider. According to Rep. Eliot L. Engel (D-N.Y.), chairman of the House Foreign Affairs Committee, the administration has not held consultations with allies nor Congress in making the decision. If Mr. Trump has serious reasons to junk Open Skies, the very least he can do is work with other signatories and Congress in a careful debate. Any such discussion would make plain to Mr. Trump that pulling out of the treaty would only help Russia by denying the United States and its allies valuable intelligence.

Arms control has been battered in recent years by mistrust and lack of political will. The INF Treaty, once heralded as reversing an arms race in Europe, is now in ruins. The next big decision is whether to extend the New START strategic nuclear weapons treaty between the United States and Russia, which entered into force in February 2011, placing limits on the most destructive nuclear weapons. An extension, not to exceed five years, is provided for in the treaty, and a decision looms early in 2021, but the administration does not appear to be paying much attention. This treaty, with its laudable verification provisions, should be prolonged. A decision to ditch Open Skies, a modest attempt at confidence-building with airplanes and cameras, bodes ill for the more serious business of controlling continent-spanning nuclear-armed missiles.

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