Armenia and Russia have signed a deal extending Russia's military presence in Armenia in exchange for security guarantees.
The deal was signed after talks between Russian President Dmitry Medvedev and Armenian President Serzh Sarkisian in Yerevan on August 20.
The deal would see the lease on a Russian military base in Armenia extended from 2020 to 2044. It also calls for Russia to provide modern weapons and equipment to Armenia's military.
The accord is likely to cause concern in neighboring Azerbaijan, which is locked in a long-simmering conflict with Armenia over the disputed Nagorno-Karabakh region.
Armenia also awarded Russia a contract to build two new nuclear reactors at a Soviet-era built nuclear power plant.
The defense pact is actually an upgrading of a 1995 treaty allowing Russian ground and air forces access to a base in the west of the country. It expands the Russian mission from protecting only the interests of the Russian Federation, to also ensuring the security of the Republic of Armenia.
Under the pact, Moscow will also supply Yerevan with modern weapons and "special" military hardware. The existing base houses MiG-29 fighter jets and S-300 missile-defense systems, as well as troops.
In an interview broadcast on Russian television before the signing, Armenian Foreign Minister Eduard Nalbandian, praised the new agreement. "We are supporting the initiative to sign this agreement which has very good elements such as equal and indivisible security for all states on the Euro-Atlantic territory and in Eurasia," he said.
A spokesman for Sarkisian's ruling Republican Party, Eduard Sharmazanov, said the new pact would not only protect Armenia's borders, but would exclude the possibility that neighboring Azerbaijan will try to settle the ongoing Nagorno-Karabakh conflict by force.
Nagorno-Karabakh, a breakaway region in Azerbaijan mainly populated by ethnic Armenians, which was the subject of a six-year war between Armenian and Azerbaijani forces. The enclave has been controlled by ethnic Armenians since a 1994 cease-fire.
Sharmazanov said the latest Armenian move to strengthen its security was in response to statements from Azerbaijan that it is prepared to retake Nagorno-Karabakh by force. He noted that in addition to having Azerbaijan along its eastern border, Armenia was facing Turkey, Baku's ally, along its western border.
But not everybody believes the new arrangement will benefit Armenia.
Analysts note the extended treaty only refers to defending Armenia, while Nagorno-Karabakh is legally part of Azerbaijan, and is therefore not covered by the treaty. Any fresh fighting involving Armenian troops would likely primarily be on the territory of Nagorno-Karabakh, not of Armenia.
Russian analyst Pavel Felgengauer says the treaty is not about Russia defending Armenia from Azerbaijan, but about warding off interference by Turkey.
Former Armenian national security adviser Gerard Libaridian, meanwhile, says the document does not even bind Russia to help Armenia, but leaves intervention to Russia's discretion.
“The 1995 treaty has a provision, which I’m sure will remain in the new one, that if there are military hostilities within Armenia’s borders Russian won’t automatically come to [Armenia's] aid," Libaridian says.
"That is, if one party [to the treaty] is subjected to attack, there will be consultations with the other. It's the other side that will decide whether or not to participate [in the war.] And I don't think that provision will be changed.”
Former Azerbaijani presidential adviser Vefa Gouluzadeh says the pact allows Russia to deepen its presence in Armenia. "Armenian territory, it is Russian territory, and Russia [is] increasing its military presence in Armenia, against NATO, against America, in case of war with Iran," he says.
Together with its bases in Georgia's breakaway regions of South Ossetia and Abkhazia, the pact gives Russia a strong military presence close to the borders of NATO member Turkey.
RFE/RL's Armenian and Azerbaijani Services contributed to this report