Russian Foreign Minister Sergei Lavrov said Russia was ready to deploy troops to the Armenia-Azerbaijan border to quell tensions between the two countries, but Yerevan's hardline position had so far prevented it.

Tensions have spiraled between Armenia and Azerbaijan over the blockade of the only road giving direct access to the disputed Nagorno-Karabakh region from Armenia in recent weeks.

Lavrov said Russia was still prepared to send a mission to the region within the framework of the Collective Security Treaty Organisation (CSTO), a Moscow-led military alliance of which Armenia, but not Azerbaijan, is a member.

But Yerevan's previous insistence on including condemnations of Azerbaijan's behavior had stood in the way.

"We had difficulties related to the situation in Armenia, when our Armenian friends pushed the need to send a CSTO mission to the border with Azerbaijan to ensure some stability there," Lavrov told a news conference on Wednesday.

"We agreed on a document and on the parameters of the mission ... but it was not possible to accept it, because Armenia started insisting that the document contain a harsh condemnation of Azerbaijan."

Russia is an ally of Armenia, but also strives for good relations with Azerbaijan.

The latest stand-off concerns a blockade of the Lachin Corridor linking Armenia to the Nagorno-Karabakh region, internationally recognized as part of Azerbaijan but controlled by its ethnic Armenian majority, with support for Armenia.

Azerbaijanis who say they are environmental activists have blockaded the road for more than a month in what they say is a dispute over illegal Armenian mining. Yerevan says they are government-backed agitators.

The impasse is being seen as a test of Russia's ability to calm hostilities in its back yard.

Officials in Armenia have grown increasingly angry at Moscow's refusal to use its peacekeeping force in the region to end the blockade, while Moscow has criticized Armenia's attempts to have the European Union broker a settlement.

"Despite the fact that we are allies ... Armenia prefers to negotiate with the European Union," Lavrov said on Wednesday.

He said any EU presence in the region without Baku's consent would be counterproductive.