Armenia said on Wednesday it would host a joint army exercise with the US next week, at a time of rising military tension with neighbouring Azerbaijan and open friction in its relationship with Russia.

The Armenian Defence Ministry said the purpose of the Sept 11-20 "Eagle Partner 2023" exercise was to prepare its forces to take part in international peacekeeping missions.

A US military spokesman said 85 US soldiers and 175 Armenians would take part. He said the Americans - including members of the Kansas National Guard, which has a 20-year-old training partnership with Armenia - would be armed with rifles and would not be using heavy weaponry.

The move comes at a time of intense Armenian frustration with its ally Moscow. Prime Minister Nikol Pashinyan has accused Russia, distracted by its war with Ukraine, of failing to protect Armenia against what he called continuing aggression from Azerbaijan.

Olesya Vartanyan, senior South Caucasus analyst at non-profit conflict prevention organisation Crisis Group, said Armenia was sending a signal to Moscow that "your distraction and the fact that you are so inactive plays towards our enemy", meaning Azerbaijan.

Despite the small scale of the exercise, Russia said it would be watching closely. It has a military base in Armenia and sees itself as the pre-eminent power in the South Caucasus region, which until 1991 was part of the Soviet Union.

"Of course, such news causes concern, especially in the current situation. Therefore, we will deeply analyse this news and monitor the situation," Kremlin spokesman Dmitry Peskov said.

Russia maintains a peacekeeping force in the region to uphold an agreement that ended a war between Armenia and Azerbaijan in 2020, the second they have fought since the Soviet collapse.

The frustration between Russia and Armenia is mutual, with Moscow this week accusing Pashinyan of "public rhetoric bordering on rudeness".

Vartanyan said that while Armenia and Azerbaijan are closer to a possible peace agreement than they have been for years, there is also a serious risk of a major new escalation between them.

Tensions are running high because of a nine-month Azerbaijani blockade of the highway linking Armenia to Nagorno-Karabakh, an enclave that is internationally recognised as part of Azerbaijan but is populated by around 120,000 ethnic Armenians.

Azerbaijan has justified its action by saying Armenia was using the road to supply weapons to Karabakh, which Armenia denies. The squeeze has led to shortages of fuel, medicine and food, including rationing of bread.

Vartanyan said footage on social media in recent days was showing increasing Azerbaijani military movements near the front line between the two countries. "It doesn't look good at all," she said.