Maduro signed an executive order that will form a "Constituent National Assembly" - a body that could make those changes.
Venezuela's current constitution permits the president to establish such a body.
Caracas residents blocked streets with trash bags, broken concrete and twisted metal Tuesday to protest the socialist president's bid to rewrite the constitution amid a deepening political crisis. "May 1 belongs to the working class", said the president. The body is controlled by the opposition. The move has been rejected by the opposition which has called on its supporters to rebel.
National Guard troops shot tear gas in a district of west Caracas towards hundreds of opposition protesters standing around waiting to march.
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.
Only half of the 500-member assembly, or less, would be elected, he said. He said some 200-250 would be elected via direct vote.
Leonel Alfonso Ferrer, a Venezuelan constitutional attorney, tells CNN en Espanol that, in the short term, nothing changes. Nicolas Maduro is not going forward, but toward the cliff.. The National Assembly Venezuelan will still be controlled by the opposition, and so on.
"The assistance was provided so far to 37 people, 30 of them suffered from various injuries, one was wounded by bird shot, three more suffered from asphyxiating gases and the same number of people felt unconscious", Muchacho wrote on Twitter.
White House advisers postpone Paris climate deal meeting
The meeting was scheduled for Tuesday. "It's been postponed", a senior official told AFP on Tuesday. President Barack Obama's government played a leading role in forging.
The opposition immediately seized on Maduro's proposal for a new charter as evidence that his mentor's revolution lies in shambles.
"I don't want a civil war", Mr Maduro told a May Day rally of his supporters in the capital, Caracas.
The opposition has responded with outrage, calling on Venezuelans to openly revolt against what it defines as a state-led coup and a constitutional fraud to entrench a dictatorship.
"What has happened today, and I say without exaggerating or trying to be dramatic, is the greatest coup in the history of Venezuela". It's Nicolas Maduro dissolving democracy and dissolving our republic.
"We, the Venezuelans, will not accept the continuation of Maduro's autocoup..." It said it was organizing a "mega protest" for Wednesday.
"So really popular pressure is the only thing they have, and possibly worldwide pressure but that too has not really wielded many results until now". The constitution is widely regarded as one of the most progressive in the world, not only enshrining broad social rights to the population, but also creating space for the population to directly intervene in political decision making beyond elections. Critics say elections have been delayed because Maduro is afraid of the outcome.
Venezuela's President Nicolas Maduro has ordered a 60% increase in the country's minimum wage, effective from Monday. But the Washington Post reports that, though protesters over the past month have been mostly middle-class citizens upset with the country's economic collapse and the government's authoritarian rule, poorer citizens are starting to join the ranks due to food shortages.