I have confidence in you... At this moment, in this country, you have no substitute

Castro (speaking to Chavez on air)

On Sunday, the two allies went a step further - singing a duet of a popular ballad on a marathon radio show in Venezuela.

Their rendition of the song Venezuela - which was somewhat off-key - came at the end of a four-hour show in which they fielded calls, continually joked with each other and discussed colonial history.

[In the audio President Chavez sings first.]

Given the antagonism towards the two men in Washington, it is unlikely that President Bill Clinton will take out his saxaphone to join them in forming a trio in the foreseeable future.

Castro practices a shot at the end of the game

The show took place in a makeshift studio in an area precious to both - the Carobobo battlefield where the South American liberator Simon Bolivar defeated the Spanish in the 19th century.

President Castro is currently on a five-day state visit to the country to sign an oil deal in which Venezuela - the world's third biggest oil exporter - will help finance Cuba's $1bn annual oil import bill.

'No substitute'

Mr Castro praised the leadership qualities of the Venezuelan president.

"I have confidence in you," he told President Chavez. "At this moment, in this country, you have no substitute."

Mr Chavez has promised to launch an ambitious new economic policy aimed at pushing through a "social revolution" for Venezuela's poor.

The two have a shared passion for leftist ideals and strongly condemn colonialism past and present.

Chavez throws a ball in the friendly baseball game with Cuba

Both oppose what they call a "unipolar" economic order dominated by the US.

On the show, they had a studious discussion of Latin American history and anti-colonial heroes.

They also joked about Cuba thrashing Venezuela by 17-6 in a friendly baseball game on Saturday.

"The only way we can successfully face up to the challenges of neoliberalism is to unite... avoiding new colonialisms," Mr Chavez said.

Mr Castro's communism and Mr Chavez's nationalism have strained relations with the US, which imposed an embargo on Cuba after the 1959 revolution.

Some opposition politicians and media have criticised Mr Castro's visit and the oil deal, saying it could further damage relations with the US, Venezuela's main oil customer.