Turkey's purchase of Russian S-400s worries Biden

American leader Joe Biden expressed concern over Turkey's acquisition of Russian S-400 anti-aircraft missile systems, the White House press service reports.

"President Biden reaffirmed our defense partnership and Turkey's importance as a NATO ally, but noted the US is concerned with Turkey’s Russian S-400 systems," the statement reads.

At the same time, the US president noted that he is ready for cooperation with Turkey and finding effective solutions. "President Biden stressed his desire to maintain a constructive relationship, expand areas of cooperation and effectively resolve differences," the White House adds.