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YEREVAN, Armenia (AP) — Armenia is freezing its ratification of an agreement to normalize ties with Turkey and reopen their shared border, the Armenian president said Thursday — dealing a setback to efforts to end the countries' long-standing enmity.

Turkey closed its border with Armenia in 1993 to protest the Armenia-backed war by separatists in the Nagorno-Karabakh region; the region is an enclave within Azerbaijan but under the control of Armenian and ethnic Armenian forces.

The border closure exacerbated tensions already high over the issue of whether the killing of up to 1.5 million Armenians during the final days of the Ottoman Empire amounted to genocide.

Neither Turkey nor Armenia have ratified the October agreement to restore diplomatic ties. Armenia's governing coalition accuses Turkey of dragging its feet by demanding the Nagorno-Karabakh dispute be settled first.

President Serge Sarkisian said Thursday he was not abandoning the normalization process, but instead would "suspend the procedure of ratifying the protocols."

"We shall consider moving forward when we are convinced that there is a proper environment in Turkey and there is leadership in Ankara ready to re-engage in the normalization process," he said in a televised address.

In Turkey, Prime Minister Recep Tayyip Erdogan said Armenia was free to decide how it wanted to proceed. "I have expressed our loyalty to the protocols on numerous occasions," he said. "We will press ahead with the process on the principle that treaties are binding."

Mediation efforts by Russia, France, the United States and the Organization for Security and Cooperation in Europe to resolve the Nagorno-Karabakh dispute have made little visible progress.

The United States urged both sides to continue to work toward reconciliation.

"President Sarkisian's announcement makes clear that Armenia has not ended the process but has suspended it until the Turkish side is ready to move forward. We applaud President Sarkisian's decision to continue to work towards a vision of peace, stability, and reconciliation," Assistant Secretary of State Phil Gordon said in a written statement.

"We continue to urge both sides to keep the door open to pursuing efforts at reconciliation and normalization," he said.