Some 30,000 people died in the Nagorno Karabakh conflict, which erupted after the mountainous region declared independence in 1991.Azeri President Ilham Aliyev has warned he is ready to use force to wrest control of a disputed enclave from Armenia if last-ditch peace talks fail.
He said talks starting on Sunday in Munich were the final hope of settling the Nagorno Karabakh issue peacefully.
A fragile ceasefire has been in place in the region since it was the scene of a brutal war between the two countries in the 1990s.
Both nations lay claim to the enclave, currently under Armenian control.
In comments broadcast on Azeri TV on Saturday, President Aliyev said that if the Munich talks failed to reach agreement he would be "left with no other option".
"We have the full right to liberate our land by military means," he said.
Western diplomats attending the talks, the latest in a round of internationally mediated meetings on the dispute, have said they hope the situation will not reach that point.
The region and seven surrounding Azeri district have been under Armenian control since the Russian-brokered ceasefire in 1994.
Azerbaijan has never ruled out military action to take back the land and has spent billions on dollars on building up its military.
The BBC's Tom Esslemont, in the South Caucuses region, says Mr Aliyev is using stronger language than ever before because the talks come at a critical time.
The meeting will be the first since Armenia and Turkey - an ally of Azerbaijan - normalised diplomatic relations after a century of hostility.
That move has left Azerbaijan feeling isolated, says our correspondent.
BBC News - Azerbaijan threatens Armenia over Nagorno Karabakh