Hugo Chavez undergoing his “most difficult hours”

President Hugo Chavez is undergoing his “most difficult hours”, Venezuela’s Vice-President Nicolas Maduro has said.

Nicolas Maduro spoke at length in a speech apparently designed to reassure citizens despite the failing health of Venezuela’s leader.

He accused the US of plotting against the Venezuelan government and said a US military attaché would be expelled.

On Monday officials said Hugo Chavez, 58, had a new, severe respiratory infection.

Dozens of people gathered to pray for his health at the hospital where Hugo Chavez is being treated.

He has not appeared in public since he returned to Venezuela last month after being treated for cancer in Cuba.

The address broadcast live on TV from the presidential Miraflores Palace showed Nicolas Maduro surrounded by political and military leaders in a display of solidarity.

Nicolas Maduro accused “enemies of the fatherland” in Venezuela and abroad, particularly the US, of seeking to undermine democracy in Venezuela.

Speaking in a room full of dignitaries including the defence minister and the president’s brother Adan Chavez, Nicolas Maduro said Hugo Chavez’s illness was an “attack” by his enemies and called for this to be investigated.

Nicolas Maduro said the US air force attaché, David Delmonaco, had been spying on Venezuela’s military and had 24 hours to leave the country: A US embassy spokesman said Washington was formulating a response.

In recent days, the opposition has condemned what they say is the lack of clarity surrounding his condition.

“The lack of precise information worries Venezuelans and fuels rumors,” said Ramon Guillermo Aveledo of the opposition Democratic Unity coalition.

At the weekend, hundreds of Venezuelan students and opposition members marched in Caracas demanding full details about Hugo Chavez’s health.

Information Minister Ernesto Villegas accused Hugo Chavez’s opponents of showing “the same hatred that they have shown towards Chavez all these years.

“It annoys them that he won’t give up and neither will the people!” he wrote on his Twitter account.

On Monday Ernesto Villegas announced from the military hospital where Hugo Chavez is being treated that he had suffered “a worsening of respiratory function” and that his condition continued to be “very delicate”.

He said Hugo Chavez was undergoing “intensive chemotherapy, as well as complementary treatments”.

“The commander-president remains clinging to Christ and to life, conscious of the difficulties that he is facing, and complying strictly with the programme designed by his medical team,” Ernesto Villegas said.

Hugo Chavez, who has been in office for 14 years, is believed to have cancer in his pelvic area, but his exact illness has never been disclosed.

He announced in June 2011 that he had cancer and has undergone four operations since then, as well as chemotherapy and radiation therapy.

The president was re-elected for another six-year term in October 2012, but the Supreme Court ruled that his swearing-in on January 10 could be delayed because of his illness.

Hugo Chavez is said to be taking decisions about the country from the hospital bed but there have been mixed messages from officials on his condition.