YEREVAN, Armenia (AP) — U.S. National Security Adviser John Bolton says Russian arms supplies to both Azerbaijan and Armenia have hampered the settlement of their conflict over the region of Nagorno-Karabakh.

Speaking Thursday on a visit to the Armenian capital, Bolton told reporters that Russian arms sales to both countries have “clearly not contributed to the resolution of the dispute because of the enormous leverage it gives Russia over both parties.”

Nagorno-Karabakh is a region of Azerbaijan that has been under the control of ethnic Armenian forces backed by Armenia since a war there ended in 1994. International efforts to settle the conflict have stalled.

Russia has sought to maintain friendly ties with both Azerbaijan and Armenia, which remain locked in a conflict over Nagorno-Karabakh.