Esper had personally told Turkish Defense Minister Hulusi Akar in Brussels on June 26 that Turkey could not have both the S-400 and the F-35 advanced stealth fighter jets.
"We are aware of Turkey taking delivery of the S-400, our position regarding the F-35 has not changed and I will speak with my Turkish counterpart Minister Akar this afternoon," Esper said at the Pentagon.
"There will be more to follow after that conversation," Esper said.