Armenia and Azerbaijan have failed to reach an agreement in their long and often violent dispute over the territory of Nagorno-Karabakh, but said they had made some progress during a summit hosted by Russia.

In a meeting Friday in the Russian city of Kazan, Armenian President Serzh Sarkisyan and his Azeri counterpart, Ilham Aliyev, were unable to agree on a basic principles agreement that would have set the stage for a settlement over the disputed ethnic Armenian enclave in western Azerbaijan.

But in a statement after the talks, which was hosted by Russian President Dmitry Medvedev, the leaders said they had reached a “mutual understanding” on a range of issues that could pave the way to signing the basic principles.

The two sides have been under increasing international pressure to sign the principles. U.S. President Barack Obama telephoned each of them Thursday to strongly encourage signing. The Russian Foreign Ministry had issued a statement also calling for an agreement.

Two decades ago, Armenia and Azerbaijan fought a war over Nagorno-Karabakh that ended in a 1994 cease-fire. Since then, talks have dragged on without resolution.

Since the 1994 cease-fire, Nagorno-Karabakh has been under the control of Armenian forces. Despite the suspension of hostilities, exchanges of gunfire continue along the borders of the disputed region.

The conflict over Nagorno-Karabakh left 35,000 dead and forced as many as 1 million people from their homes.

Repeated international efforts to broker a peace deal have failed.