CARACAS, Venezuela (AP) - Venezuela's embattled president issued a decree Monday for writing a new constitution, ratcheting up a political crisis that has drawn hundreds of thousands of anti-government protesters into the streets.

President Nicolas Maduro gave no details on how members would be chosen for a planned citizen assembly to produce a new charter, though he hinted some would selected by voters. Many observers expect the socialist administration to give itself the power to pick a majority of delegates to the convention.

Opposition leaders immediately objected, charging that writing a new constitution would 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.

A demonstrator aims a fire bomb during an opposition May Day march in Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government May Day demonstrations as an intensifying protest movement enters its second month. (AP Photo/Ariana Cubillos)

Speaking hours after another big march demanding his ouster ended in clashes between police and protesters, 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," Maduro 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 citizens assembly. That could distract them from the drumbeat of 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."

The constitution was last rewritten in 1999, early in the 14-year presidency of the late Hugo Chavez, who began Venezuela's socialist transformation.

The leader of the opposition-controlled National Assembly, Julio Borges, called the idea of a constitutional assembly a "giant fraud" by Maduro and his allies designed to keep them in power at any cost. 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.

Earlier Monday, anti-Maduro protesters tried to march on government buildings in downtown Caracas, but police blocked their path - just as authorities have done more than a dozen times in four weeks of near-daily protests. Officers launched tear gas and chased people away from main thoroughfares as the peaceful march turned into chaos.

Opposition lawmaker Jose Olivares was hit in the head with a tear gas canister and was led away with blood streaming down his face. 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 unrest of the past month and hundreds have been injured.

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 widespread shortages of food and other basic goods, violence on a par with a war zone, and triple-digit inflation. Maduro accuses his opponents of conspiring to overthrow him and undermine the country's struggling economy.

The move to rewrite the constitution underscored many protesters' chief complaint about the administration: That it has become an unfeeling dictatorship. Sergio Hernandez, a computer technology worker who attended 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.

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Hannah Dreier on Twitter: https://twitter.com/hannahdreier. Her work can be found at https://www.ap.org/explore/venezuela-undone .

A Bolivarian National Guard water cannon puts out a gasoline bomb that fell on an armored vehicle during an opposition May Day march in Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government May Day demonstrations as an intensifying protest movement enters its second month.. (AP Photo/Ariana Cubillos)

FILE - In this Jan. 18, 2017, file photo, Venezuela's President Nicolas Maduro speaks during a press conference at Miraflores presidential palace in Caracas, Venezuela. President Maduro called on Monday, May 1, for a citizens congress and a new constitution, as he faces an escalating political crisis. (AP Photo/Ariana Cubillos, File)

Police fire tear gas at demonstrators during an opposition May Day march in Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government May Day demonstrations as an intensifying protest movement enters its second month. (AP Photo/Ariana Cubillos)

Demonstrators clash with security forces at an opposition May Day march in Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government May Day demonstrations as an intensifying protest movement enters its second month. (AP Photo/Ariana Cubillos)

An opponent to President Nicolas Maduro holds a sign that reads in Spanish "Maduro dictator," referring to President Nicolas Maduro, at an opposition May Day march in Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government May Day demonstrations as an intensifying protest movement enters its second month. (AP Photo/Ariana Cubillos)

A woman screams after a man was run over by a police motorcycle during skirmishes between protesters and police at a May Day opposition march in eastern Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government demonstrations as an intensifying protest movement enters its second month. (AP Photo/Fernando Llano)

A woman shouts during a May Day march by opponents of President Nicolas Maduro in eastern Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government demonstrations as an intensifying protest movement enters its second month. (AP Photo/Fernando Llano)

A protester scuffles with police as others shout: "Police don't support the dictatorship" during a May Day opposition march in eastern Caracas, Venezuela, Monday, May 1, 2017. Venezuelans are taking to the streets in dueling anti- and pro-government demonstrations as an intensifying protest movement enters its second month. (AP Photo/Fernando Llano)