The United States and Russia are urging the leaders of Armenia and Azerbaijan to come to an agreement in their long and often violent dispute over the territory of Nagorno-Karabakh at a summit hosted by Russia.

Armenian President Serzh Sarkisyan and his Azeri counterpart Ilham Aliyev meet Friday in the Russian city of Kazan, hosted by Russian President Dmitry Medvedev.

The two sides have come under increasing international pressure to sign a basic principles agreement that would set the stage for a settlement over the disputed ethnic Armenian enclave in western Azerbaijan.

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

U.S. President Barack Obama phoned each of the leaders Thursday and strongly encouraged them to sign the basic principles. The president said that now is the time for a settlement for a “better future” for citizens of both countries.

The Russian foreign ministry has issued a statement also calling for an agreement.

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 a million people from their homes.

Repeated international efforts to broker a peace deal have failed.