Yes or no.

That's the choice for Cubans as they vote Sunday on whether to approve a new constitution for the first time since 1976.

The new version would launch modest economic and social changes while maintaining the one-party socialist system.

(SOUNDBITE) (Spanish) CUBAN, MAYDA TOYO, SAYING: "It's an act of reaffirming the revolution, to keep up the legacy of everyone who has given their lives for our homeland and to continue to defend its ideals." The proposed changes in the constitution include recognition of private property, foreign investment, small business, gender identity and the right to legal representation upon arrest.

After casting his ballot in Havana, Cuban President Miguel Diaz-Canel told reporters the vote comes at a critical time, as the deepening crisis in Venezuela brings its ally into the crosshairs of the U.S. (SOUNDBITE) (Spanish) PRESIDENT MIGUEL DIAZ-CANEL, SAYING: "We know what we're going through at the moment with the imperialist threat.

There is an intention to impose a capitalist and neoliberal platform in Latin America, using the most perverse practices, the vilest things." Observers say they expect around three quarters of voters to ratify the new constitution.

Dissidents and exiles meanwhile campaigned to reject the constitution because it entrenches communism.

Results will be announced on Monday.