Turkish Defence Minister Hulusi Akar in March said that despite some issues, Turkish pilots were continuing their training at an air base in Arizona on the F-35, each of which costs $90 million, and that Ankara was expecting the aircraft to arrive in Turkey in November.
Pence also criticized Germany for building a natural gas pipeline that connects its country to Russian Federation, saying the move would turn Germany into a "captive of Moscow".
Pompeo gave the warning to Turkish Foreign Minister Mevlüt Çavuşoğlu Wednesday in Washington during the first day of the two-day NATO Ministerial, State Department Spokesman Robert Palladino said in a statement.
At his Senate Armed Services Committee nomination hearing to lead U.S. European Command, Air Force Gen. Tod Wolters called the co-location of the F-35 and the S-400 "absolutely unsustainable".
"Germany must do more".
This week Turkey also released footage of its new hypersonic rail gun which China, the U.S. and Russian Federation have all sort to develop.
The Trump administration has halted its sale of F-35 fighter jets to ally Turkey until the country agrees to cancel its purchase of an anti-aircraft missile system from Russian Federation, according to reports. The potential economic opportunities between Turkey and the United States were also a focus of the discussion.
Turkish Foreign Minister Mevlut Cavusoglu repeated that the deal with Russian Federation - thought to be worth about £2.5bn (£1.9bn) - would not be cancelled.
Following protracted efforts to purchase air defense systems from the USA with no success, Ankara decided in 2017 to purchase the Russian S-400 air defense system.
In a PBS Newshour interview broadcast on Wednesday, Cavusoglu said Ankara proposed "to form a technical working group and to examine" any U.S. concerns over the S-400s.
Turkey, however, has said the system is insufficient for its needs.
"Turkey must choose, does it want to remain a critical partner in the most successful military alliance in the history of the world, or does it want to risk the security of that partnership", Pence said at "NATO Engages: The Alliance at 70", an event hosted by the Atlantic Council in Washington. Eight Turkish companies are involved in supplying parts for the fighter jet, worth up to $12 billion in business, according to Lockheed Martin, the aircraft's maker.
"The radar is an electronic intelligence collection platform", said Aaron Stein, director of the Foreign Policy Research Institute's Middle East program.
In Washington, Turkish Foreign Minister Mevlut Cavusoglu repeated his government's stance that the purchase of the S-400 is a "done deal", but sought to reassure allies that it will not pose a threat to the military alliance. "This is not a choice for us", he said.
(Chip Somodevilla/Getty Images) Acting Defense Secretary Patrick Shanahan (2nd L) listens to President Donald Trump during a bilateral meeting with NATO Secretary General Jens Stoltenberg in the Cabinet Room at the White House, April 2, 2019. We do not want a new Cold War. "We are prepared for that option", he said.