The replacement candidate put forward by the opposition, former Prime Minister Vazgen Manukyan, is expected to deliver a speech.
People protest against what they consider unfavorable terms of the Nagorno-Karabakh peace deal that Pashinyan signed last month on the back of a 1.5-month armed conflict with Azerbaijan.
The Armenian opposition parties formed a coalition and demanded that Pashinyan step down. They elected Manukyan to temporarily assume the prime minister's duties and call a snap election in which he himself would not run as a candidate.
The trilateral declaration was signed by the leaders of Armenia, Azerbaijan and Russia on 9 November. The deal entailed significant territorial concessions to Azerbaijan, which many in Armenia and Armenian-populated Nagorno-Karabakh were not happy about given the death toll of thousands, predominantly young, people. The fighting stopped on 10 November, with the sides terminating at effectively occupied territories. Russian peacekeepers have been deployed to Nagorno-Karabakh to monitor the truce.