NATO Secretary-General Anders Fogh Rasmussen arrived Thursday in Armenia, his first visit to the country.
In a speech to students at Yerevan State University, Rasmussen expressed support for Armenia's partnership with the NATO alliance.
"It's an opportunity we must seize because we all have to gain and so does the region as a whole," he said.
Armenia went to war with Azerbaijan over the disputed territory of Nagorno-Karabakh. Tensions rekindled in June when fighting broke out between Azeri and Armenian forces over the region.
Rasmussen is to visit Azerbaijan Friday. He called on both sides to break down barriers that interfere with reconciliation.
"There must be no return to conflict between Armenia and Azerbaijan," he said. "Tensions must be reduced and concrete steps must be taken to promote regional cooperation and reconciliation."