The mountainous route across Azerbaijan has been blocked since Dec. 12, when protesters claiming to be environmental activists stopped traffic by setting up tents. Some 120,000 ethnic Armenians in Nagorno-Karabakh depend on it for supplies of food, fuel and medicine.

The standoff has raised international concern, with U.S. Secretary of State Antony Blinken calling on Monday for the immediate reopening of the route.

Russian is the main power broker in the region and has peacekeeping troops stationed along the Lachin corridor. Their failure to reopen it is a source of frustration for Armenia.

Russia "continues painstaking and difficult work with both Armenia and Azerbaijan," Kremlin spokesman Dmitry Peskov told reporters when asked to comment on Blinken's remarks. He did not elaborate.

Armenia says the protest was orchestrated by the Azerbaijani government as a deliberate blockade of Nagorno-Karabakh. Azerbaijan denies that, saying the activists are staging a legitimate protest against illegal mining activity.

The two countries have fought two wars since the 1991 collapse of the Soviet Union over Nagorno-Karabakh, which is internationally recognised as part of Azerbaijan but populated mainly by ethnic Armenians.

(Reporting by Filipp Lebedev, Writing by Caleb Davis, Editing by Mark Trevelyan)