A Russian S-400 surface-to-air missile system. Sergei Malgavko | TASS via Getty Images

NEW DELHI — 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. The S-400 system is believed to have a larger range than the American-made THAAD missile system and is estimated to cost significantly less. Turkey is slated to receive the S-400 next year and is expected to have the system ready for war by 2020. Meanwhile, all of that comes as Congress is inching closer to blocking the transfer of two F-35 jets to Turkey.

The stealth fighter jets that hang in the balance

A U.S. Air Force F-35 Lightning II joint strike fighter approaches at Eglin Air Force Base, Florida. U.S. Air Force photo by Samuel King Jr.

Turkey, an F-35 program partner, is currently slated to receive two of the jets. That delivery of Lockheed Martin's fifth-generation jets is the start of what Ankara hopes will eventually amount to 100 of the stealth aircraft. In June, the U.S. defense giant held a formal hand-off ceremony at its F-35 facility in Fort Worth, Texas. After the ceremony, Lockheed ferried the aircraft to Luke Air Force Base in Arizona where Turkish pilots began training alongside U.S. airmen. The Russian-made S-400 missile system, which is equipped with eight launchers and 32 missiles, is capable of targeting stealth warplanes like the F-35 fighter. In the colossal $717 billion National Defense Authorization Act, Congress tasked the Pentagon to deliver a report in 90 days outlining the potential risks associated with Turkey's purchase of the S-400 missile system. "We are going through this current issue between us, and we are engaged in, I would call it, frequent, right now, very frequent, discussions at very high levels to try to sort this out," Defense Secretary James Mattis said Tuesday when asked about the F-35 sale to Turkey. "I believe that there is sincerity on both sides to try to work this out. So we're engaged in it right now, and I — you know, I need to work with them directly on this, as does Secretary (of State Mike) Pompeo and others on our side," he added. What's more, tensions between the U.S. and Ankara have intensified over the detention of American pastor Andrew Brunson.

US pastor Andrew Craig Brunson escorted by Turkish plain clothes police officers arrives at his house on July 25, 2018 in Izmir. AFP | Getty Images