Armenia and Azerbaijan were locked in conflict over Nagorno-Karabakh for nearly four decades after the Soviet Union they were both members of collapsed.

But hurdles remain. Azerbaijan also said Armenia’s constitution must “eliminate the claims against the sovereignty and territorial integrity of Azerbaijan,” as a prerequisite to allow for the signing of the peace treaty.

Armenia and Azerbaijan have agreed on the text of a peace agreement, potentially ending over 35 years of conflict, though Azerbaijan has set several preconditions before signing.