Venezuelan opposition leaders have called for a 24-hour nationwide strike to pressure the socialist government after more than seven million people rejected a plan to rewrite the constitution and consolidate the ruling party's power.
The country has been stricken by shortages, inflation and more than 100 days of clashes between protesters and police.
The opposition also said the National Assembly, which it controls, would name new members to the government-dominated Supreme Court, setting up a showdown with President Nicolas Maduro, whose party controls all but a few state institutions.
Opposition parties also plan to sign a declaration calling for the formation of an alternative "government of national unity", a step towards total rejection of government authority.
"Overall the package is pretty radical, especially the idea of a parallel government," said David Smilde, a Tulane University expert on Venezuela. "I think it could lead to real chaos within the government."
He noted that the opposition moves were to be implemented in phases over the next week, starting with the nationwide strike on Thursday, giving both sides the opportunity to negotiate possible concessions.
Earlier in the day, opposition parties floated the idea of escalating more than three months of street protests, which have left at least 93 people dead and 1,500 wounded.
More than 500 protesters and government opponents have been jailed.
"Right now we have to escalate and deepen this street movement," National Assembly president Julio Borges told local radio station Exitos ahead of Monday's opposition announcement, which was delayed for hours as government opponents discussed their next steps behind closed doors.
Speaking at a news conference, opposition leader Freddy Guevara made little mention of more protests, a sign that the opposition had decided to change tactics after Sunday's vote.
"We call on the whole country to launch a 24-hour national strike this Thursday, a massive, non-violent protest, as a way to pressure the government and to prepare for the final steps, which will be next week, to confront this fraud on the constitution and to restore constitutional order," he said.
The opposition said 7,186,170 Venezuelans participated in Sunday's symbolic referendum rejecting Mr Maduro's plans for the July 30 election of an assembly that would remake the country's political system.
Mr Maduro's allies have called on the assembly to impose executive branch authority over the few remaining institutions outside the control of Venezuela's socialist ruling party.