This op-ed ran in Defense One on July 13, 2018.

As the NATO summit comes to an end, the focus turns to President Trump’s upcoming meeting with Vladimir Putin. Congress has shown that our NATO alliance remains paramount, and President Trump ultimately expressed his support to our allies by signing the Brussels Summit Declaration. Now is the time for the president to convey to Putin that duplicitous behavior is unacceptable and our long-term commitment to NATO will not waiver.

I recently returned from meetings in Moscow, Oslo, and Helsinki, where everything I heard reinforces my belief that a unified NATOalliance is essential to American security and prosperity. The concerns relayed to me by European leaders underscore the fear our European friends have about Russia’s activities. My colleagues and I reassured them of America’s commitment to our joint security during our meetings, and additionally, the Senate this week overwhelmingly passed a motion that reaffirms our nation’s assurance to NATO.

Putin is not our friend – he is an adversary intent on continuing Russia’s disruptive activities in Europe and the Middle East, and against us here at home. Throughout Europe, Russia funds efforts to undermine the sanctions jointly imposed by the United States and Europe. In the Middle East – both in Syria and Libya – Russia’s involvement is escalating the refugee crisis Europe is struggling to contain. Further afield, our military leaders testify, Moscow is supporting the Taliban in Afghanistan. And of course, Russia interfered with our own democratic process in 2016and will continue the same efforts in upcoming elections.

I share President Trump’s desire for better relations with Russia. My purpose for traveling to Moscow was to begin a dialogue to explore how we can develop a responsible relationship. In every meeting I attended in Moscow, I made clear the Russians must end their election meddling here in the United States and Europe in order to open the door to rebuilding relations. I brought up Russia’s destabilizing support for separatists in Ukraine and its illegal seizure of Crimea after Ukraine democratically chose a president who sought closer ties to the West. Its support for the Taliban undermines the democratic government in Afghanistan. In every circumstance, Russian officials, including Foreign Minister Sergey Lavrov, continued to obfuscate or outright deny any responsibility. However, those meetings left me unconvinced that Russia is prepared to change its behavior.

Click here to read the full op-ed in Defense One.