Turkey's deal to buy missile defense systems from Russia is not causing problems with NATO, U.S. Air Force Secretary Heather Wilson suggested on Tuesday.

Speaking at a panel, titled "Strengthening US Alliances," in the Atlantic Council, a Washington D.C.-based think tank, Wilson stated that the U.S. has always wanted its allies to buy equipment that will work as a partner with NATO and won't pose a threat to the organization. Instead, she suggested that America's strict export controls could be a reason behind Ankara's decision to purchase from Russia. She said America's strict export policy could be causing issues with its allies. For example, the U.S. will not sell unmanned aerial vehicles due to export controls, so its allies are forced to purchase them from China, which creates a problem.

Turkey signed an agreement with Russia last December to buy S-400 surface-to-air missile batteries as part of Ankara's plans to boost its defense capabilities amid threats from PKK and Daesh terrorists at home and conflicts across its borders in Syria and Iraq.

The move to buy S-400s, which are incompatible with the NATO systems, has unnerved some NATO member countries, which are already wary of Moscow's military presence in the Middle East, prompting NATO officials to warn Turkey of unspecified consequences. Wilson said the U.S. needs to figure out how to a better ally, for example by "building things that are designed to be exportable from the very beginning so that we can all operate out of the same equipment rather than create problems." Wilson said Turkey's purchase presents some operational problems, which the departments of state and defense are discussing with Ankara.