Venezuelan self-proclaimed president Juan Guaido appealed to other countries Monday to help stop Nicolas Maduro's government from continuing to ship crude oil to Cuba.

"We have decreed no more shipment of petroleum to Cuba," Guaido said while presiding over a session of the opposition-controlled National Assembly. "Moreover, not only do we decree it, but we request international cooperation to make this measure effective."

Cuba, Venezuela's closest ally for the last two decades, receives roughly 100,000 barrels per day of crude from the oil rich nation on generous terms under the PetroCaribe program, which offers similar benefits to other countries in Central America and the Caribbean.

In the case of Cuba, payment for the oil mainly takes the form of services and the provision of doctors to staff a program extending health care to under-served areas of Venezuela.

But Guaido said Monday that the crude oil sent to Cuba is needed in Venezuela to address a nationwide power blackout now in its fourth day.

The assembly voted in favor of Guaido's proposal to declare a state of emergency in response to the protracted outage.

The leftist Maduro government blames the blackout on a cyber attack targeting the control systems at the Guri Dam, a massive hydroelectric complex in the southern state of Bolivia that supplies nearly 70 percent of Venezuela's electricity.

It is not clear that holding back crude oil exports would have any impact on the domestic energy situation.

The New York Times reported recently that US economic sanctions against the Maduro administration "have affected Venezuela's ability to import and produce the fuel required by the thermal power plants that could have backed up the Guri plant once it failed."

The United States, which has been at odds with Venezuela since Maduro's late predecessor and mentor, Hugo Chavez, took office in 1999, immediately recognized Guaido when he declared himself acting president on Jan. 23.

Guaido has since been recognized by more than 40 other countries, including much of Latin America and the major European powers with the exception of Italy.

Washington and its allies agree with the Venezuelan opposition that Maduro's re-election last May lacked legitimacy.

China, Russia and India are among the more than 100 nations that continue to recognize Maduro.