Turkish President Tayyip Erdogan said it was too early to comment on Ankara's possible purchase of additional Russian weapons in view of the Ukrainian crisis.

"In the current circumstances, it would be premature to talk about what will happen in the future. We must maintain our friendship with Mr. Zelenskyy and Mr. Putin," Erdogan said.

Turkey is in talks to buy a second batch of S-400s from Russia. Washington warned its NATO ally against buying new weapons from Russia.

"We have done for Ukraine what NATO member states have not done despite Russia, and we have continued that support. Similarly, with our humanitarian aid, we sent more than 50 trucks to Ukraine and we continue to send them," Erdogan said.