A constitutional assembly controlled by supporters of President Hugo Chavez declared a legislative emergency today and took over most functions of the Venezuelan Congress.

The move took away Congress's right to pass laws and limited its duties to a narrow range of activities such as budget oversight. It was the latest development in a growing confrontation between the assembly -- elected last month at Chavez's urging to write a new constitution for Venezuela--and the normal legislative and judicial branches of government, some of whose officials accuse Chavez of a power grab.

Chavez, a former coup leader, was elected president on a promise to bring a "social revolution" to Venezuela, and he has set out with vigor to do so. He has said the constituent assembly is the country's supreme power, but opposition leaders say it has already overstepped its bounds.

"The constitutional assembly does not have the authority to do this," said Timoteo Zambrano, head of the opposition Democratic Action Party. "This invasion creates a large vacuum and insecurity."

Congressional leaders said they will cut short a legislative recess and reconvene on Friday to discuss the move. But the constitutional assembly president, Luis Miquilena, said the assembly will not permit Congress to reconvene. The assembly, he said, has "the means" to impede it.