By JUAN FORERO
 
CARACAS, Venezuela, March 1 — A campaign by opposition groups for a recall referendum to try to oust President Hugo Chávez appeared on the brink of collapse on Monday.

Opposition leaders, expecting election officials to disqualify enough of the 3.4 million signatures they have collected for a recall to keep the measure off the ballot, accused Mr. Chávez of influencing the process.

Protesters battled national guard troops across the country in antigovernment demonstrations that began Friday and have gained momentum.

On Monday, young men threw bottles at government troops and burned tires to block streets, and at least in one Caracas district, broke into a shop and destroyed property. The country's privately owned television stations, which have sided with the opposition against the left-leaning president, beamed pictures of chaos throughout the day.

National guard troops have fought back with tear gas and armored vehicles. Two people have died since Friday and several dozen have been hurt, several of them critically.

"Why are the people in the street?" asked Henry Ramos, leader of the Democratic Action Party and an opponent of Mr. Chávez. "Because they see that the government is trying to steal their democratic rights."

Government officials accused the opposition, including municipal officials in Caracas, of fomenting violence and inflating the troubles to destabilize the country.

"There are politicians with government duties who appear to be functioning as leaders of urban guerrillas because they are going against the peace and security," Gen. Jorge Luis García Carneiro, the defense minister, told the government's Venpres news agency.

The opposition has tried to dislodge Mr. Chávez, a populist who won office in 1998, through a short-lived coup in 2002 and four big national strikes. Nothing has worked, and since last year the broad-based opposition movement has worked for a referendum.

But on Monday, the probability of a vote seemed slim as the five-member National Electoral Council disputed with the Carter Center, which is based in Atlanta, over whether the American group would continue its role as a mediator here.

The president of the council, Francisco Carrasquero, held a news conference to announce that the Carter Center was leaving the country. Jennifer McCoy, the center's representative, said she planned to stay.

"I want to make it clear that the Carter Center mission remains in Venezuela," she told reporters.

Even so, the opposition has had little luck in trying to prod the council into altering a preliminary decision that hundreds of thousands of signatures were flawed.

Under the constitutional provision for a recall vote, 2.4 million valid signatures are required to place it on the ballot. The opposition collected 3.4 million signatures. (Venezuela's popuation is 25 million.)

But election officials were expected to invalidate 400,000 signatures and to require additional verification of a million others. That would bring the number of validated signatures below the required total.

The council has said a million signatures could go through a five-day "repair period," starting on March 18, in which citizens could confirm that they had signed at one of the 1,000 sites nationwide. But diplomats monitoring the process and opposition leaders said the process is so challenging technically that it could end any chance of a referendum.

Some opposition leaders expressed disappointment with the Organization of American States, which had brokered a deal between the government and its opponents that the opposition leaders thought would lead to a recall vote. "They told us that this was the quickest path," said Antonio Ledezma, an opposition leader.

Mr. Chávez, in a fiery speech on Sunday, said his government would recognize the signatures and would permit a referendum if enough signatures were "repaired." But opponents continued to assert that the new measure was nothing more than a delaying tactic aimed at ensuring that Mr. Chávez remained in power.

Under the country's electoral guidelines, if the recall takes place after Aug. 20, Mr. Chávez's vice president could finish out his term. Opponents fear that if that happens, Mr. Chávez would rule from behind the scenes while campaigning to win the next presidential elections, in 2006.

The Bush administration, which has clashed repeatedly with Mr. Chávez, has expressed support for a recall vote.

On Monday, Scott McClellan, the White House spokesman, said, "The focus should remain on the efforts by the Venezuelan people to exercise their constitutional and democratic rights, and on the efforts to try to resolve the political polarization through a transparent and internationally monitored presidential recall referendum."