Russia’s saber rattling in reaction to a U.S. cruise missile strike on a Syrian airbase was to be expected. For the most part, it was nothing about which to be concerned.

But one of Moscow’s actions is exceedingly worrisome. After the U.S. attack, Russian officials said they were severing a “deconfliction” mechanism that has been in place since 2015.

After Russian forces moved into Syria to help that country’s regime turn back attacks by armed opponents, Moscow and Washington agreed to the system. It is intended to avoid an accidental war between our two countries.

Both U.S. and Russian warplanes operate over Syria. Sometimes, pilots of both countries are involved in offensive missions. Sometimes, their goals conflict; the United States supports some of the very militants Russian pilots attack.

To avoid accidental confrontations, the “deconfliction” system was set up. It allows each nation to warn the other of situations in which our aircraft could come into close enough proximity to be dangerous.

U.S. officials have insisted the Russians would not sever the “deconfliction” hotline. Moscow maintained it would do so.

A top priority of U.S. diplomacy should be to convince Vladimir Putin to keep the conflict avoidance mechanism in place. The very last thing either side should risk is a war between our two great powers begun by accident, when a Russian pilot and and American pilot are surprised by each other — and react decisively.