Basking in the success of a massive opposition march, Venezuela's largest labor group threatened to call a general strike to oust President Hugo Chavez.

Carlos Ortega, head of the 1 million-member Venezuelan Workers Confederation, said Thursday's march by an estimated 600,000 people proved that Venezuelans want Chavez to abandon the presidency.

Ortega told thousands of protesters holding a vigil outside a Caracas military base that his organization, which includes thousands of state workers, could call an indefinite strike. He refused to say when a decision would be made.

A previous general strike led to an opposition march April 11 in which 18 people were killed, many allegedly by pro-Chavez gunmen. The bloodshed prompted generals to oust the leftist Chavez on April 12. Chavez was restored to power April 14 after an interim government abolished the constitution.

Venezuela's main opposition parties demand Chavez leave power well before the 2007 end of his term. They have brought court cases alleging corruption are organizing a referendum on his rule and are demanding justice for the April 11 victims.

"We are on a war footing," Ortega said.

Many Venezuelans believe the country is hopelessly divided and ungovernable under Chavez, who has built a cult of personality among the poor. They say he has accumulated too much power by railroading through constitutional changes and appointing military commanders to important government posts.

They also say he has alienated the United States by cozying up to Cuba and Iraq, has mismanaged the country's oil industry, and has created a virtual private militia of neighborhood committees that intimidate dissenters. Meanwhile, the country is mired in recession.

Hundreds of thousands of Venezuelans — laborers and business executives, leftist and conservative parties — marched Thursday to remember the victims of April 11. Caracas police chief Emigdio Delgado estimated the crowd at 600,000 people.

It was a powerful show of strength against Chavez, whose power base is the 80 percent of Venezuelans who live in poverty.

After the march, government and opposition leaders accused each other of trying to provoke chaos — underscoring the political divide that grips this South American nation and global oil exporter.

Luis Francheschi, head of the National Assembly's labor committee, accused Ortega of sabotaging government-sponsored reconciliation talks.

"The government is the country's biggest employer. A strike of this magnitude can only be intended to collapse the government," Francheschi said.

"The government is completely certain of its stability," said Interior Minister Diosdado Cabello. "We have no doubts about our popular support."

Thursday's march followed a peacemaking mission this week by former U.S. President Jimmy Carter. Carter's efforts were rebuffed by Chavez's opposition, including Ortega. But Carter did convince Chavez to accept an international role in mediating Venezuela's crisis.

Opponents insist Chavez, a former paratrooper who staged a failed 1992 coup and was elected in 1998, must be replaced. They are organizing a referendum that will seek to shorten his term.

The government and the opposition accuse each other of provoking the April violence. Investigations into who committed the slayings have stalled.

Chavez told a military ceremony in the central city of Maracay that April 11 "was a dark day in our history when a privileged minority plotted to overthrow the constitutional government and install tyranny."