YEREVAN, Armenia (AP) — Armenia’s leader said Tuesday he would not take part in next week’s summit of a Moscow-led security alliance, the latest in a series of moves suggesting a growing strain in relations with longtime ally Russia.

A statement from the office of Prime Minister Nikol Pashinyan said he informed Belarusian President Alexander Lukashenko that he would not attend the Nov. 23 summit of the Collective Treaty Security Organization in the Belarusian capital, but did not give details.

The CSTO is made up of Russia, Kazakhstan, Kyrgyzstan and Tajikistan, along with Armenia and Belarus.

Since the 1991 collapse of the Soviet Union, Armenia and Russia have been allies and Armenia hosts a Russian military base, but rifts have widened over the past year.

A 2020 war between Azerbaijan and Armenia over the Nagorno-Karabakh Armenian separatist region ended with a Russia-brokered armistice under which a Russian peacekeeping force was deployed in the region. But Armenia was unhappy that the peacekeepers did not break Azerbaijan’s blockade of road travel to Nagorno-Karabakh even though keeping the link open was part of their mandate.

Armenia in turn angered Russia by voting to join the International Criminal Court, which this year indicted Russian President Vladimir Putin for alleged war crimes connected with the war in Ukraine.

Pashinyan this year canceled CSTO exercises that were to be held in his country, and in October declined to attend a summit of the Commonwealth of Independent States where Putin made his first trip outside Russia and occupied Ukraine since the ICC indictment.