President Hugo Chavez has accused his opponents of representing US interests and trying to stir up discontent in Venezuela's military while he undergoes cancer treatment in Cuba.
Mr Chavez addressed the nation on television twice by phone, saying he was in bed receiving a fourth consecutive day of chemotherapy and expected to return to Venezuela soon.
He mocked his opponents, saying their coalition is "of the United States".
"All of those attacking the Armed Force are subordinated to imperialism," Mr Chavez said, using the formal name for the Venezuelan military. "They're following the orders of imperialism, trying to divide the Armed Force, trying to demoralise it."
He did not give details but referred to recent criticisms of some top generals by opponents, and he warned his foes: "Leave the Armed Force alone." Mr Chavez said the military's response to any provocations from his opponents should be to notify state intelligence agencies and remain unified.
The opposition coalition responded with a statement saying the president's remarks "show the tension that exists within the government".
"The head of state should worry about what's happening within his government," the opposition coalition said. "The message is for you, Mr President: Leave the Armed Force alone. Don't oblige Venezuelan soldiers to say slogans in favour of you or your political ideology."
After two days without speaking publicly, Mr Chavez appeared eager to assert himself both in domestic and international affairs. He said he was sorry to see the unrest in London. He referred to the US government's debt woes and said: "The empire is sinking."
"It's a terrible crisis they have. It's capitalism," Mr Chavez said. Mr Chavez urged his military to be ready for any possible conflict like those in Libya and Syria. He reiterated his long-standing concerns about a potential conflict with the United States, saying: "They're like a wounded lion."
As for his cancer treatment, Mr Chavez said his body has been responding well. He underwent surgery in June to remove a tumour from his pelvic region, and says the chemotherapy aims to ensure that no malignant cells reappear.