* President has not been seen in a month
* Chavez missed Jan. 10 inauguration ceremony
* Top court says he can be sworn in later
Venezuela's Vice President Nicolas Maduro will fly to Cuba on Friday to visit cancer-stricken Hugo Chavez, a month after the socialist leader underwent his fourth operation in 18 months.
The 58-year-old president has not been seen nor heard from since the surgery, and has suffered multiple post-operative complications including a severe lung infection.
He missed his own inauguration on Thursday, but the Supreme Court said he could be sworn in later - in theory meaning he could remain in office for weeks or months from a Havana hospital. There has been no firm evidence he is conscious.
"I'm going to give our commander-president the good news about how the people are working, making revolution with courage, discipline and enthusiasm," Maduro said in a televised broadcast.
Argentine President Cristina Kirchner, a friend and ally of Venezuela's socialist leader, was visiting Cuba on Friday and said on Twitter she planned to take Chavez a Bible.
The vice president said Peru's President Ollanta Humala - whom he called another "comrade in arms" of Chavez - was also expected in Havana on Friday.
Unlike after Chavez's previous cancer operations in Cuba, the government has published no photos or video of the former soldier's recovery. Neither has he made any of his normally frequent phone calls back home to Venezuelan state television.
While Maduro has said he spoke to Chavez by telephone and in person during a previous visit to Havana, his comment on Dec. 24 that the president had been up walking and doing exercises was met by derision from many in the South American country.
Perhaps more than anything, the silence from the normally garrulous leader famous for his lengthy diatribes has led many to believe his 14 years in power may be coming to an end.
In his absence, government officials were forced to postpone a ceremony on Thursday to swear him in for the new six-year term that he won at a presidential election in October.
A clutch of Latin American and Caribbean leaders attended a rally that went ahead in Caracas regardless, where thousands of red-shirted loyalists held aloft copies of the constitution and were symbolically sworn-in in Chavez's place.
His condition is a top concern of officials in Cuba and other allied nations whose leftist governments have long benefited from years of Chavez's oil-fueled generosity.
Maduro, a former bus driver and union leader who shares his boss's radical views, is in charge of day-to-day government until there is clarity over whether the president will return.
He has sought to imitate Chavez's bombastic rhetoric in speeches, but struggles to emulate the folksy charisma of the president, who grew up in humble surroundings and became one of the world's best-known heads of state.
Venezuela's opposition leaders are furious at what they see as a Cuban-inspired manipulation of the constitution by Maduro and other top "Chavista" figures aimed at preventing the naming of a caretaker president due to Chavez's absence.
Should Chavez die or have to step down, a new election would be called and would likely pit Maduro against opposition leader Henrique Capriles, the 40-year-old governor of Miranda state.