WASHINGTON, April 23 (Reuters) – The U.S. government said it is "deeply concerned" by Azerbaijan establishing a checkpoint on the only land route to the contested region of Nagorno-Karabakh, saying it undermines efforts toward peace in the region.

"The United States is deeply concerned that Azerbaijan’s establishment of a checkpoint on the Lachin corridor undermines efforts to establish confidence in the peace process," the U.S. State Department said in a statement on Sunday.

The State Department urged free and open movement of people and commerce on the Lachin corridor and also called on the parties "to resume peace talks and refrain from provocations and hostile actions along the border."

Nagorno-Karabakh is internationally recognised as part of Azerbaijan, but its 120,000 inhabitants are predominantly ethnic Armenians and it broke away from Baku in a war in the early 1990s.

Azerbaijan on Sunday said it had established a checkpoint on the road leading to Karabakh due to what it cast as Armenia's use of the road to transport weapons, a step that was followed by claims of border shootings by both Azeri and Armenian forces.

Armenia said the checkpoint at the Hakari bridge in the Lachin corridor was a gross violation of the 2020 ceasefire agreement which ended a 2020 war.

Armenia called on Russia to implement the agreement, which states that the Lachin corridor, the only road across Azerbaijan that links Armenia to Nagorno-Karabakh, must be under Russian peacekeepers' control.

Nagorno-Karabakh was the focal point of two wars that have pitted Armenia against Azerbaijan in the more than 30 years since both ex-Soviet states achieved independence. Russia and Armenia are officially allies through a mutual self-defence pact, but Moscow also seeks to maintain good relations with Azerbaijan.