Venezuelans waited up to four hours for gasoline and stocked up on food and water Monday as a strike seeking President Hugo Chavez's ouster created shortages at markets, banks, pharmacies and service stations.

The growing shutdown increased pressure on Chavez to give in to opposition demands to call a referendum on his government or resign. Already, the eight-day strike has crippled the oil industry -- the world's fifth-largest and Venezuela's main source of revenue.

Strike leader Carlos Ortega said the action will continue until Chavez leaves office.

"The people you never listened to are going to oust you," Ortega said, referring to Chavez.

Gas, drinking water and cash at automatic teller machines were increasingly scarce in Caracas and other cities. Dozens of domestic flights were canceled. Banks closed. Motorists waited in a mile-long line for gas in the central city Valencia.

Jose Perez, a liquor store manager, tended to dozens of customers -- but they weren't looking for alcohol.

"People are only coming to ask if we've got water or soft drinks," Perez said. "We've got enough right now, but water might be gone today."

Production at Venezuela's two largest refineries, Paraguana and El Palito, was paralyzed, said Ali Rodriguez, president of the state-owned oil monopoly Petroleos de Venezuela S.A.

Also, the Jose refinery in eastern Venezuela could shut down within 48 hours, maintenance director Luis Torres said.

The oil industry produces 30 percent of Venezuela's $100 billion gross domestic product and 70 percent of export earnings.

Rodriguez insisted the government, which ordered the military to seize private truck fleets, was guaranteeing gasoline supply. He said nearly 1.6 million gallons arrived in Caracas on Monday.

Rodriguez urged strikers to end their "sabotage," warning that shortages and electricity blackouts were imminent. The government could be forced to pay $6 billion to creditors if the company defaults on its debts, he said.

"We are threatened with a national disaster," Rodriguez said in a televised address.

Dozens of treasury and customs agents joined the opposition strike, which began Dec. 2.

Harbor pilots and cargo handlers closed Venezuela's biggest port, Puerto Cabello, 90 miles west of Caracas, said Jorge Serrano, president of the National Ports Institute. Puerto Cabello handles most of Venezuela's non-oil imports and exports.

The United States, which consumes more than half of Venezuela's exported oil, urged opposition and government delegates to resume talks sponsored by the Organization of American States. Delegates began meeting with OAS Secretary General Cesar Gaviria late Monday.

Venezuela's crisis caused international oil prices to rise Monday. January heating oil rose 1.09 cents to 75.82 cents per gallon on the New York Mercantile Exchange. January crude increased 27 cents to $27.20 a barrel.

Citing economic and political turmoil, Venezuela's opposition had demanded that Chavez call a nonbinding referendum on his presidency in February. After three people were killed and 28 wounded at an opposition rally Friday, strike leaders demanded that Chavez either call a binding referendum on his presidency or resign.

Chavez, a populist former army paratrooper elected in 1998 and re-elected in 2000, refuses to call elections that could cut his term, which ends in 2007 -- though he has offered to take on challengers in a binding referendum next year.

The president accuses strikers and Venezuela's news media of inciting a coup. Chavez was briefly ousted in April by dissident military officers after a general strike and the slayings of 19 people at an opposition march.

Polls suggest the leftist Chavez has the steadfast support of up to 45 percent of Venezuela's poor majority, based on his "peaceful revolution" to eradicate poverty. Many supporters are organized in neighborhood "Bolivarian Circles," ready to take to the streets to defend their president.

But his overall popularity has plunged to 30 percent because of the shrinking economy and unrest.

So far, the armed forces have supported the president, despite calls for rebellion from more than 100 officers who have been demonstrating at an eastern Caracas plaza since October. After a popular rebellion restored him to power in April, Chavez purged the military and placed loyalists in top positions.

Chavez's government struggled to control Petroleos de Venezuela. But officials had yet to find a qualified crew to replace that of the PDVSA-owned tanker Pilin Leon, which since Wednesday has refused to deliver more than 11.4 million gallons of gasoline to the city of Maracaibo.

PDVSA harbor pilots warned that Venezuela could lose an international safe shipping certification without qualified crews. That means foreign ports would have to refuse Venezuelan deliveries, they said.

"You have to bring in ships, tugboats, crews, operators, and there's no plan yet," Jorge Kamkoff, an oil monopoly vice president told Dow Jones Newswires.

Oil company managers also complained that Chavez street activists were harassing strikers. In Maracay, armed Chavez activists assaulted at least seven journalists covering the strike, El Siglo newspaper reported.