Turkey is in the process of constructing a site for a Russian missile system despite warnings from the United States to not buy the platform, according to a source with firsthand knowledge of an intelligence report covering the subject.

The assessment, published a month ago, included satellite imagery of a concrete launch facility as well as bunkers, according to the source, who spoke on the condition of anonymity. The new construction fits the pattern for Russia's S-400 surface-to-air missile system, the source indicated.

Last year, Ankara signed an agreement with Moscow for S-400 missiles, a deal reportedly worth $2.5 billion. Since then, Turkey's march toward procuring the Russian missile system has raised concerns among NATO partners, who are wary of Moscow's increasing military presence in the region.