Russia sees Istanbul as a "comfortable place" to conduct diplomacy with the United States but does not yet believe Washington has adopted a constructive approach in talks, the RIA Novosti news agency cited Russia's Deputy Foreign Minister Sergei Vershinin as saying on Monday.
Turkish President Tayyip Erdogan has emerged as a key broker between Russia, Ukraine and the United States since Russia invaded Ukraine on Feb. 24.
Several rounds of diplomacy, including failed early peace talks, the Black Sea grain initiative, prisoner exchange negotiations and a face-to-face meeting between Russian Foreign Intelligence Service chief Sergei Naryshkin and CIA Director William Burns have taken place in Istanbul or the Turkish capital Ankara.