"It's time to bring Eta directly into a rapid, verifiable, and effective disarmament process by making it a concrete proposal," the regional government said in a statement.
The Basque government — backed by the Basque parliament — proposed the creation of a commission to which Eta would send information on the exact location and state of its arsenal.
"The sealed storing of arms without verification or a timetable serves nothing," declared the Basque government led by the nationalist PNV party.
It said that by dealing directly with Eta with the objective of bringing an end to its violent struggle for independence, the regional government was recognizing "the will of the majority of Basque society."
Eta is blamed for the killing of 829 people in a four-decade campaign of bombings and shootings for an independent Basque homeland in northern Spain and southwest France.
Spain, like France, has steadfastly refused negotiations with the group and insists Eta should formally disarm and disband without conditions.
The regional Basque government has expressed vexation with Madrid's lack of response, and has repeatedly called on the conservative government of Prime Minister Mariano Rajoy to recognize the disarmament pledge and engage with Eta.
Also on Sunday, the International Verification Commission (CIV), composed of international conflict resolution experts, confirmed Eta had made progress in its disarmament efforts.
The CIV — which is not recognized by the Spanish government to verify the disarmament program Eta announced last March — said in a statement it had received materials proving the group had continued decommissioning arms and munitions, and placed them in sealed depots.
After its March disarmament pledge drew no response, Eta said in July it was dismantling its "logistics and operational networks" to further negotiations on the sentences and incarceration conditions of the 493 Eta members imprisoned in Spain and France.