* President had not been seen since Dec. 11 cancer surgery
* Government says he is breathing through a tracheal tube (Adds cancer expert, paragraphs 16-19)
By Daniel Wallis and Marianna Parraga
CARACAS, Feb 15 (Reuters) - Venezuela published the first photos of cancer-stricken Hugo Chavez since his surgery in Havana more than two months ago and said the socialist president was breathing through a tracheal tube and struggling to speak.
The pictures showed the 58-year-old, smiling but with his face looking swollen, lying down in a hospital bed and flanked by his two daughters. In one, they were reading Thursday's edition of the Cuban state newspaper, Granma.
The photos were shown by Chavez's son-in-law, Science Minister Jorge Arreaza, who has been traveling between Havana and Caracas to be at the Venezuelan president's bedside.
He said Chavez - whose political identity is built around long-winded speeches, meandering talk shows and casual chatter with supporters - was having trouble talking.
"He doesn't have his usual voice," Arreaza told Venezuelan state television. "He has difficulty communicating verbally, but he makes himself understood. He communicates his decisions perfectly. He writes them down."
Chavez has not appeared in public, and has still not been heard from, since the operation on Dec. 11, his fourth surgery for cancer in his pelvic region first diagnosed in mid-2011.
Neither the pictures nor the new details on his condition offer solid clues as to when Chavez might be able to return home, or whether the disease will force him to step down.
Allies appear content to let Chavez continue governing silently from Havana indefinitely. They bristle when asked about how the long the unusual arrangement could last.
The former soldier has never disclosed what type of cancer he has been treated for, and critics have accused government officials of secrecy over his condition.
"A few days ago the liars said they were speaking with the president. Now they say he can't talk!" opposition leader Henrique Capriles wrote on Twitter. "They are playing around with their own people."
Chavez was re-elected for a new six-year term in October after appearing to have staged a remarkable recovery from the disease following three earlier operations and weeks of grueling chemotherapy and radiation sessions.
But he soon had to fly back to Cuba for more medical tests, then another round of complex surgery. He was too ill to return to Venezuela for his inauguration ceremony last month.
The government, which said the new photos were taken on Thursday night, added that he has respiratory problems.
"The post-operative respiratory infection was controlled, but there is still some insufficiency," it said in its latest official communique on the president's health.
"Under these circumstances, which are being treated, the commander is currently breathing through a tracheal tube."
Experts say patients who are put on a ventilator after surgery usually have a tube inserted in their mouths. If the tube is there too long it can irritate the upper part of the windpipe and doctors may need to replace it with a tracheotomy.
"Those patients are getting the tracheotomy because they still need the ventilator, they are still hooked up to a breathing machine," said Dr. Michael Pishvaian, a gastrointestinal cancer specialist at Georgetown University's Lombardi Comprehensive Cancer Center in Washington.
Pishvaian, who is not treating Chavez, said experts assumed the Venezuelan leader was suffering from a soft tissue sarcoma.
"The most common place they spread to is the lungs. The possibility of him having significant disease in the lungs that is impairing his lung function and making it hard for him to get off the ventilator is a very plausible scenario."
Venezuelan Vice President Nicolas Maduro - Chavez's preferred successor - said earlier this week his boss was undergoing "tough" and "complex" alternative treatments, but gave no details.
If Chavez dies or has to resign, the authorities would have to call a new vote within 30 days. That would likely pit Maduro against Capriles, the 40-year-old governor of Miranda state who lost to Chavez in last October's election.
Maduro has sought to copy Chavez's fierce rhetoric against his rivals, and on Friday he again took aim at Capriles: "This loser's heart is so bad it makes him mad that President Chavez is well," Maruro told reporters.
Amid so much uncertainty, some in Venezuela's opposition believe Cuba's Fidel and Raul Castro - close allies of Chavez - could be pulling strings behind the scenes.
About 20 student protesters chained themselves together near the Cuban embassy in Caracas on Thursday, demanding details on his condition. Maduro said Capriles and others in the "neo-fascist" opposition would be responsible for any violence there.
For many critics Maduro's words were an echo of Chavez's combative style, harsh criticism of the United States and radical leftist policies, including widespread nationalizations, which they say have crippled the OPEC nation's economy.
However, Chavez's brand of oil-fueled welfare spending and folksy charisma have also won him a near-religious following among many poor Venezuelans. Supporters reacted to the new pictures with joy, tweeting: "Chavez lives and smiles!"
"Chavez's smile is the smile of the children, of the mothers, the young, the soldiers and the men. It's the smile of the fatherland," said Diosdado Cabello, the powerful head of the National Assembly and an ex-army buddy of the president.
The normally loquacious Chavez's silence since his surgery has convinced many Venezuelans that his extraordinary 14 years in power could be coming to an end.
His son-in-law Arreaza, however, described a light-hearted mood around the president who, he said, enjoyed receiving visitors in his hospital room where he listened to music from his rural boyhood home in Venezuela's central plains.
"It's a party," Arreaza told state TV. (Additional reporting by Mario Naranjo in Caracas and Julie Steenhuysen in Chicago; Editing by Brian Ellsworth and Christopher Wilson)