FILE PHOTO: U.S. Secretary of State Rex Tillerson (R) walks with Russian Foreign Minister Sergey Lavrov before their meeting at the State Department in Washington, U.S., May 10, 2017. REUTERS/Yuri Gripas /File Photo

MOSCOW (Reuters) - U.S. Secretary of State Rex Tillerson has given assurances that Washington’s only goal in Syria is fighting Islamic State, the TASS news agency cited Russian Foreign Minister Sergei Lavrov as saying on Thursday.

Lavrov said he had last had a telephone conversation with Tillerson on Oct. 9, the agency reported.

Russia’s defense ministry accused the United States on Tuesday of pretending to fight Islamic State and of deliberately reducing its air strikes in Iraq to allow the group’s militants to stream into Syria to slow the Russian-backed advance of the Syrian army.

Lavrov, touching upon a possible U.S. withdrawal from the Iran nuclear deal, said it was hard to imagine how it could be legally implemented, TASS reported.