Venezuelan President Nicolas Maduro postponed the launch of a powerful new "constituent assembly" to Friday, pushing it back a day in the face of international accusations of undermining democracy and opposition calls for massive protests.

"It has been proposed that the installation of the National Constituent Assembly, instead of being held tomorrow, be organized in peace and calm, with all necessary protocol, on Friday at 11:00 am (1500 GMT)," Maduro said at a ceremony for the new body's members.