President Hugo Chavez on Friday wrapped up his campaign to push through broad constitutional changes with a broadside attack against adversaries at home and abroad — including a threat to cut off oil exports to the United States.

Chavez told a crowd gathered in the center of Caracas that if the referendum was approved and the result was questioned — "if the 'yes' vote wins on Sunday and the Venezuelan oligarchy, playing the [U.S.] empire's game, comes with their little stories of fraud" — then he would order oil shipments to the United States halted Monday.