The head of the Turkish air force said on Saturday his country’s decision to buy a $3.4 billion missile defence system from a Chinese company was not final, and could still change.

General Akin Ozturk, commander of the Turkish Air Force, also said he did not see any linkage between Turkey‘s interest in buying F-35 fighter jets built by Lockheed Martin Corp and the missile defence procurement process.

Asked at a global gathering of air chiefs about U.S. concerns that the Chinese system would not be interoperable with those of NATO members, Ozturk said, “This is not the last position of Turkey. It may change.”