ANKARA, June 12 (Xinhua) -- Turkish President Recep Tayyip Erdogan on Wednesday said he would discuss Ankara's purchase of Russian S-400 missile defence system with his U.S. counterpart Donald Trump in G20 summit in Japan late this month.

"I will meet with President Donald Trump in Japan at the end of the month. I hope there will be a mutual discussion of these issues," Erdogan said in a televised speech at the ruling Justice and Development (AK) Party's group meeting.

Erdogan also said he would like to talk about the issue by phone with the U.S. ahead of two leaders' meeting in Japan.

Last week Pentagon announced in a letter to Turkish Defence Minister Hulusi Akar that if Turkey does not drop the Russian S-400 missile defence system by July 31, Ankara would be blocked from purchasing F-35 fighter jets.

Turkish president insisted that Turkey has already bought the Russian S-400 missile defense systems, adding it is a done deal.

Addressing the U.S. plans to wind down Ankara's involvement in the F-35 fighter jets program over the purchase, Erdogan stressed that Turkey was not only a client but also a production partner that invested over 1 billion U.S. dollars in the project.

The U.S. repeatedly warned it will cut off Ankara's purchase of F-35 fighter jets if the Turkish government goes ahead with plans to buy Russian S-400 air defense system, triggering a heated dispute between the two NATO allies.

Washington has already suspended deliveries of parts and services related to Turkey's receipt of the multi-million dollar jets.