Venezuelan President Hugo Chavez on Friday threatened to cut off oil exports to the United States if it "goes over the line".
"Attempts by the United States to isolate and blockade Venezuela failed over the past years, and will continue to fail in the future, as they are unreasonable," Chavez said in a statement.
Chavez's latest comments are in response to remarks by U.S. Secretary of State Condoleezza Rice on Thursday that the Venezuelan government posed one of the biggest problems in the region.
Testifying before the International Relations Committee of the U.S. House of Representatives, Rice also called for an international "united front" against Venezuela, whose relationship with Cuba, she said, was "a particular danger to the region."
"We are talking with others to try and make certain that there is a kind of united front against some of the kinds of things that Venezuela gets involved in," she said.
Chavez accused Rice of being "moonstruck" to make those comments, which he said would jeopardize efforts to reduce tensions in relations between the two countries.
Diplomats from the United States and Venezuela met here Friday, hoping to mend diplomatic relations between the two countries, which have reached their most tense levels ever.
U.S. Ambassador William Brownfield said that Venezuela's National Assembly President Nicolas Maduro and a team from the Western Hemisphere Department of the U.S. State Department had met for a "very fruitful" talk, both on issues where Washington and Caracas agreed, and those on which they differed.
U.S.-Venezuelan relations hit a new low earlier this month after Venezuelan authorities accused a U.S. naval attache at the embassy in Caracas of spying and expelled him from the country. Washington responded by sending home a Venezuelan diplomat.