Venezuelan President Hugo Chavez is suffering from a new, severe respiratory infection following cancer surgery, the government has said.
Many Venezuelans have been demanding full details about Mr Chavez's health
Information Minister Ernesto Villegas said Chavez's condition continued to be very delicate.
Chavez, 58, returned to Venezuela last month after being treated for cancer in Cuba, but has not appeared in public since.
Many Venezuelans have been demanding full details about his health.
Villegas read out the latest brief update on national television.
Speaking from the Caracas military hospital where Chavez is being treated, Villegas said: "Today there is a worsening of respiratory function."
He said Chavez was undergoing "intensive chemotherapy, as well as complementary treatments".
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 10 January could be delayed because of his illness.
At the weekend, hundreds of Venezuelan students and opposition members marched in Caracas demanding full details about President Chavez's health.
He is said to be taking decisions about the country from the hospital bed but there have been mixed messages from officials on his condition.
Vice President Nicolas Maduro said on Saturday that Chavez was still having chemotherapy.
On Thursday, Maduro had gone on TV to say Chavez was battling for his life.