Updated

Venezuela's opposition accused Hugo Chavez's government of harassing its leaders and vowed to escalate a nationwide strike until Chavez calls presidential elections.

Chavez refused to budge, and his ministers accused strike leaders of trying to provoke a coup. With pressure rising in Venezuela, a top oil supplier to the United States, the U.S. State Department urged the government and opposition to restart negotiations.

"An agreement to hold national elections at a mutually agreed upon time is in our opinion the only true solution to Venezuela's political crisis," spokesman Robert Zimmerman said Monday.

Venezuela's opposition launched the strike Monday and claimed an 80 percent success rate, even though many businesses remained open and oil production and exports weren't immediately affected. Thousands banged pots and pans late Monday to voice their support for the strike.

Strike organizer Carlos Ortega, head of Venezuela's largest labor confederation, said the action would continue at least through Tuesday — though more extensions were widely expected.

"Why extend for 24 hours a strike that has failed?" asked Vice President Jose Vicente Rangel, reiterating government claims that Monday's action didn't affect key industries and services.

Interior Minister Diosdado Cabello accused the strikers of attempting a coup and said the government won't permit "another April 11."

On that day, Ortega and other opposition figures staging a similar anti-Chavez general strike called an opposition march in which 19 people were killed, many by pro-Chavez gunmen. Dissident officers ousted Chavez on April 12 and loyalists restored him two days later when an interim government abolished the constitution.

Ortega on Monday denounced anonymous threats against strike leaders and the arrests of a handful of strike activists. He demanded immediate elections and a demilitarization of Caracas' police department.

Chavez ordered an army takeover of the police Nov. 16, citing labor troubles within the department. Critics called it a show of Chavez's increasing authoritarianism.

Last month, Venezuela's opposition delivered 2 million signatures demanding a nonbinding referendum on Chavez's rule — hoping to increase pressure on Chavez to resign.

The National Elections Council set a Feb. 2 vote, but the Supreme Court quashed the vote on legal technicalities.

Chavez insists Venezuela's constitution allows only a binding vote halfway into his presidency, August 2003.

Minor unrest was reported around the country, including protesters burning tires in central Maracay and the National Guard firing tear gas at civilians protesting the arrest of an opposition lawmaker and strike organizer in western San Cristobal. In Maracaibo, shopkeepers were harassed by roaming bands of Chavez supporters.

The state-owned oil monopoly Petroleos de Venezuela S.A. insisted operations were normal. But Fedepetrol, the country's biggest federation of oil workers' unions, said 82 percent of oil workers stayed home.

Oil accounts for half of government income and a third of gross domestic product. The industry's involvement could make or break the protest.

A prolonged strike at the oil company, or a move by Chavez to replace strikers, could have disastrous effects on Venezuela's already weak economy.

In Caracas and Maracaibo, motorists lined up at service stations after strike leaders claimed gasoline shortages were imminent.