A U.S. official, speaking on the condition of anonymity, suggested on Friday that a Turkish purchase of Russian missile defense systems could present an opportunity for U.S. forces.
"It's shocking that Russia, however, isn't more worried about sending their equipment to a NATO nation, co-located with U.S. forces, where it can be studied and where we are likely to gain valuable intelligence," the official said.
"It may certainly be a unique opportunity," the official added.
Turkey's purchase of the Russian surface-to-air S-400 system has led to significantly strained ties with Washington, which earlier this week suspended delivery of parts and services necessary to Turkey's receipt of the F-35 stealth fighter jet.
U.S. officials have suggested Turkey buy the U.S. Patriot missile system rather than the Russian S-400 system, arguing it is incompatible with NATO systems and exposes the F-35 to possible Russian subterfuge, including covert efforts to obtain critical information on the jet, which could then be relayed to Russia.
In response to U.S. concerns, Çavuşoğlu said Wednesday the system would be for Turkey's use.
"It doesn't have to be integrated into the NATO system, and this is not our aim. It is for our own use," he said. "This system will not see any NATO system, including F-35s, as an enemy."
The Pentagon said Wednesday it transferred the third of Turkey's F-35 jets to Luke Air Force Base in Arizona, with a fourth to be delivered Friday.
Turkish pilots are currently training on the advanced fifth-generation fighter jet at the base, and the Pentagon said their training will continue despite the suspension of parts and services announced on Monday.
Turkey joined the F-35 Joint Strike Fighter Program in 2002 and has invested more than $1.25 billion. It also manufactures various aircraft parts for all F-35 variants and customers.