HAVANA — A health scare for Venezuelan President Hugo Chavez, who underwent surgery for cancer in Cuba, has generated deep concern in the Americas' lone communist country which depends politically and economically on him.

Chavez, 56, has been in Cuba for three weeks. Officials say he has undergone two rounds of surgery, the first to treat a pelvic abscess and another to extract a cancerous tumor.

"Hopefully, nothing will happen to him. Without Chavez, things in Cuba would get extremely rough again like before. We would be back to blackouts," said Elisa Castellanos, a 68-year-old housewife.

'Before' refers to the period before Chavez was first elected president in 1999. His arrival to power meant that post-Cold War communist Cuba, politically adrift and its economy in tatters after losing the East bloc support it depended on for three decades, got a new lease on life.

The lease has lasted a decade; now Chavez's mortality potentially could be its demise.

Venezuela became isolated Cuba's main political ally -- supporting and helping fund regional economic and media initiatives -- and its main economic partner and underpinning.

Critically, Chavez's Venezuela has provided cut-rate oil to Cuba, which Havana otherwise would be hard-pressed to afford. That has kept Cuban power plants on line mostly after years of maddening blackouts.

Venezuela now provides Cuba with 100,000 bpd of its crude -- just over half Cuba's consumption.

Cuba in turn also sends almost 40,000 teachers and doctors to Venezuela for whose services the Cuban government is paid as contractor before it compensates its workers.

Venezuela's state oil giant PDVSA meanwhile is helping Cuba explore its waters so it can tap its own significant reserves in the Gulf of Mexico. If Cuba is able to meet its own energy needs and even sell oil, its regime could project itself decades into the future.

Venezuela is involved in Cuban projects small and big, like remodeling and refitting the oil refinery in Cienfuegos, Cuba, and building a fiber optic cable for high-speed Internet. Their cooperation also is tight on food supplies, technology, transportation, and tourism.

Their 10-year-old close cooperation, which generates about six billion dollars a year for Cuba -- the island's top source of income -- and is without precedent in Latin America.

The arrangement quietly riles the United States, whom the leftist allies decry as an "imperialist" peril.

Chavez's portrait is a common sight on political billboards on roads and even in barbershops across Cuba, alongside images of revolutionary icon Fidel Castro, 84, and President Raul Castro, 80.

The Venezuelan president has kept support strong even after a then-ailing Fidel Castro handed power to his brother Raul in 2006. Just June 8, Chavez signed another cooperation agreement worth 1.3 billion dollars.

"Chavez is our brother, he is Fidel's son. We love him a lot, he is really another Cuban, a Cuban leader. He gives us oil, highways, cooperation," Maria Gamito, a retired teacher, told AFP.

Raul Castro is implementing some small economic reforms, mostly decentralizing and allowing more self-employment. But he also has refused to embrace China-style capitalism, and any political opening.

"The relationship with Venezuela is the most strategic one the Cuban government has," Arturo Lopez-Levy at the University of Denver, told AFP.

It can survive without Chavez, but under much tougher circumstances, he stressed.