The U.S. has yet to respond to Turkey's proposed working group to address concerns about the Russian S-400 missile defense system, a Turkish deputy foreign minister said Wednesday.

Yavuz Selim Kıran was in Washington as part of a delegation that includes Çağrı Erhan, a member of the Turkish Presidential Security and Foreign Policy Committee, and journalist Bora Bayraktar.

The delegation arrived Monday for a series of talks in Washington and New York to increase awareness of U.S.-Turkish relations as well as dispelling misinformation on the subject.

Speaking to Turkish reporters at the Turkish Embassy, Kıran said Ankara has been taking Washington's concerns into consideration regarding the Russian defense system.

"We are sure that this [working group] will dispel America's concerns and render discussions that the S-400 system will jeopardize the F-35's presence pointless," Kıran said. "And we are open to any kind of diplomacy and dialogue on this issue."

In early April, Foreign Minister Mevlüt Çavuşoğlu said Turkey proposed Washington establish a technical working group to make sure the S-400 system would not pose a threat to the F-35 fighter jets or NATO systems.

Kıran said his delegation met six American lawmakers to convey Turkey's reasons on the S-400 purchase as well as the U.S.' long-standing inaction to provide Ankara with necessary air defense systems, referring to the Patriot missiles.

"We witnessed that the senators and U.S. Congress members did not have much information about the background of this purchase," he noted.

Tensions between the U.S. and Turkey have reached a fever pitch in recent months with Turkey set to begin receiving the advanced S-400 Russian surface-to-air missile system, which Washington said will jeopardize Turkey's role in the F-35 fighter jet program and could trigger congressional sanctions.

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

The U.S. is still trying to dissuade Turkey from purchasing the Russian-made missiles, but Ankara has on a number of occasions voiced its determination to go through with the deal.

In due consideration of regional and global developments that pose grave risks to its national security, Turkey decided to meet its need for an air defense system from Russia and inked a $2.5 billion deal with Moscow in December 2017 after the U.S. repetitively rejected selling Patriot missiles to Turkey.

U.S. officials advised Turkey to buy the U.S. Patriot missile system rather than the S-400 from Moscow, arguing the Russian system would be incompatible with NATO systems and expose the F-35 to possible Russian subterfuge.

Turkey, however, emphasized the S-400 would not be integrated into NATO systems and would not pose a threat to the alliance.

In the meantime, Defense Minister Hulusi Akar late Tuesday said Turkish military personnel are currently in Russia, participating in training on how to use the Russian missile system.

Akar also said Turkey is making preparations for the potential implementation of the Countering America's Adversaries Through Sanctions Act (CAATSA).