Venezuela's socialist leader has ordered the writing of a new constitution, further angering opponents whose intensifying campaign to oust him has brought hundreds of thousands into the streets to demand change. President Nicolas Maduro was vague in a televised speech Monday evening about how members would be chosen for a citizen assembly to produce a new charter. He hinted some would selected by voters, but many observers expect the government to give itself the power to pick a majority of delegates to the convention. Opposition leaders cried foul, calling the planned constitutional assembly a ploy to give Maduro an excuse to put off regional elections scheduled for this year and a presidential election that was to be held in 2018. Polling has suggested the socialists would lose both those elections badly amid widespread anger over Venezuela's economic woes of triple-digit inflation and shortages of food and other goods. An opposition activist clashes with the riot police during a march against President Maduro held on May Day Speaking hours after yet another big anti-government march ended in rock throwing by some protesters and tear gas firing by police, Maduro said a new constitution is needed to restore peace and stop the opposition from trying to carry out a coup. "This will be a citizens assembly made up of workers," the president said. "The day has come brothers. Don't fail me now. Don't fail (Hugo) Chavez and don't fail your motherland." If the constitutional process goes forward, opposition leaders will need to focus on getting at least some sympathetic figures included in the assembly. That could distract them from organizing the near daily street protests that they have managed to keep up for four weeks, political analyst Luis Vicente Leon said. "It's a way of calling elections that uses up energy but does not carry risk, because it's not a universal, direct and secret vote," Leon said. "And it has the effect of pushing out the possibility of elections this year and probably next year as well." Venezuela's constitution was last rewritten in 1999, early in the 14-year presidency of the late Hugo Chavez, who began the socialist transformation of the oil-exporting nation. The president of the opposition-controlled National Assembly, Julio Borges, called a constitutional assembly a "giant fraud" by Maduro and his allies designed to keep them in power. Borges said it would deny Venezuelans the right to express their views at the ballot box, and he urged the military to prevent the "coup" by Maduro. "What the Venezuelan people want isn't to change the constitution but to change Maduro through voting," he said at a news conference in eastern Caracas, where anti-government protesters once again clashed with police Monday. Anti-government protests have been roiling Venezuela for a month, and Borges said more pressure is needed to restore democracy. He called for a series of street actions, including a symbolic pot-banging protest Monday night and a major demonstration Wednesday. On Monday, anti-Maduro protesters tried to march on government buildings in downtown Caracas, but police blocked their path, as authorities have done more than a dozen times the past four weeks. Officers launched tear gas and chased people away from main thoroughfares as the peaceful march dissolved into chaos. Some demonstrators threw stones and gasoline bombs and dragged trash into the streets to make barricades. A separate government-sponsored march celebrating May Day went off without incident in the city. At least 29 people have died in the political unrest of the past month and hundreds have been injured. Opposition lawmaker Jose Olivares was hit in the head with a tear gas canister Monday and was led away with blood streaming down his face. People of all ages and class backgrounds are participating in the protests. The unrest started in reaction to an attempt to nullify the opposition controlled-congress, but has become a vehicle for people to vent their fury at Venezuela's economic problems and violent crime. Maduro blames the economy's troubles on sabotage by his opponents and accuses them opponents of conspiring to overthrow him. The move to rewrite the constitution underscored a chief complaint that many protesters make about the government: That it has become an unfeeling dictatorship. Sergio Hernandez, a computer technology worker who participated in Monday's protest, said he would not return to his normal life until Maduro's administration had been driven out. "We're ready to take the streets for a month or however long is needed for this government to understand that it must go," he said. An opposition activist takes part in a march against President Nicolas Maduro