The talks are being held at the US consul general's residence and come after this month's first high-level meeting between the two nuclear powers since the start of Russia's Ukraine offensive.
Neither has said who would participate, but Russia's state TASS agency said the Russian delegation included "foreign ministry representatives".
US President Donald Trump has sought to reset relations with Moscow since coming to office last month, reaching out to Russian counterpart Vladimir Putin and initiating high-level talks with Kremlin officials for the first time in over three years.
Russian Foreign Minister Sergei Lavrov and US Secretary of State Marco Rubio met on February 18 in the Saudi capital Riyadh, where they agreed to kickstart talks on the Ukraine conflict, without involving Kyiv.
The United States sided with Russia twice Monday in votes at the United Nations, seeking to avoid condemnation of Moscow's military assault on its neighbour three years ago.
The talks in Istanbul are aimed at normalising the work of their diplomatic missions, after each expelled embassy staff from the other during former US president Joe Biden's administration.
NATO member Turkey has sought to play a role in negotiations to end hostilities in Ukraine, twice hosting direct negotiations between Moscow and Kyiv in March 2022.