Venezuelan Vice-President Nicolas Maduro is heading a meeting of political and military leaders as concern mounts over President Hugo Chavez's health, state media says.
On Monday officials said he had a new, severe respiratory infection.
Dozens of people gathered to pray for Mr Chavez's health at the hospital where he is being treated.
Mr Chavez, 58, returned to Venezuela last month after being treated for cancer in Cuba.
The defence minister and the president's brother Adan Chavez were reportedly among those at the meeting chaired by Vice-President Nicolas Maduro at the presidential Miraflores Palace.
The meeting is being broadcast live on state TV. Mr Maduro accused "enemies of the fatherland" in Venezuela and abroad, particularly the United States, of seeking to undermine democracy in Venezuela.
He went on to say that Mr Chavez's illness was an "attack" by his enemies and called for this to be investigated.