Armenian and Azerbaijani officials said on Thursday that they had agreed the text of a peace agreement to end nearly four decades of conflict between the South Caucasus countries, a sudden breakthrough in a fitful and often bitter peace process.

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.

The European Union says conclusion of Azerbaijan and Armenia talks and agreement on the text of a possible treaty, "a decisive step."