With government officials predicting that President Hugo Chavez's allies won all 167 seats in the National Assembly, opposition parties that boycotted nationwide elections said Monday they would forge a strategy to effectively challenge the volatile Venezuelan leader.

Leaders of the splintered opposition had encouraged voters to stay home on Sunday, charging that the National Electoral Council was controlled by the president's supporters and that electronic ballot machines could violate voter confidentiality. Opposition leaders said the slim voter turnout -- officially listed at 25 percent -- was a show of strength and proved that the legislative sweep did not reflect the will of the public.

Although no official results have been made public, the election win appeared to give Chavez more than the two-thirds majority needed to alter the constitution. Some allies have called for a change that would allow Chavez to run for a third six-year term in 2012 without the need for a referendum. Chavez has already announced his plans to run for reelection in 2006.

Oil revenue pouring into the world's fifth-largest oil-producing nation has allowed Chavez to fund a wide range of social programs that have pushed his popularity to 68 percent, according to an October poll by the Venezuelan firm Datanalisis.

Interpretations of the election varied widely. Analysts said the result had created new challenges and opportunities for both Chavez and his foes. Opposition parties, which were fractured and already had a diminished voice in the legislature, said their apparent loss of all National Assembly seats would free them to rebuild and mount a more unified challenge to Chavez. The government, analysts said, will have to convince the public that the election constitutes a clear mandate before instituting constitutional changes and new laws.

"I think this marks a clear turning point that will mean the separation of the old opposition and the birth of a new generation of leadership," said Julio Borges, a 2006 presidential candidate of the Justice First party, which pulled out of the elections last week. "No one can say that we emerged as winners, but the government didn't win either. The low turnout sent a message that the people don't have confidence in the country's institutions and its leadership."

Borges said opposition parties have a clear deadline: They must determine a new strategy before the presidential election in July. Borges, the leading opposition presidential candidate in recent opinion polls, said he hopes that members of other opposition parties will now back him. Borges is one of several party leaders seeking to unify the opposition behind their candidacies.

"There have already been some meetings because they are in a hurry to offer a new organizational structure before the elections," said Alfredo Keller, a Caracas-based pollster and analyst. "It could be an opportunity for them to motivate the electorate, and I think we'll see a lot of movement in that direction in the next few months."

Many opposition leaders have complained that they already had been reduced to marginal roles in the National Assembly, in which parties aligned with Chavez held a narrow majority with 86 seats. They said that Chavez had maneuvered with allies to push through legislation that allowed him to politically control the country's legal system and effectively silence the opposition media.

Opposition leaders cast doubt Monday on the official voter turnout figures, asserting that the number was closer to 15 percent. Election monitors from the European Union and the Organization of American States had not yet released their findings on Monday.

Chavez has gained widespread support among the country's poor by advocating a social revolution, and has accused the United States of imperialist intervention.

Chavez, a former army officer, has also accused U.S. officials of plotting to assassinate him and to invade Venezuela. His allies launched an advertising campaign before the election urging voters to cast ballots in a show of support for the government's efforts to combat such threats.

Critics said the election showed a weakening of public support for Chavez because they said many of those who did not vote included Chavez supporters.

"Most of the advertising before the election was designed to get people out to the polls to help defend Chavez against the external threat of the United States," said Argelia Rios, a political analyst in Caracas. "Because his supporters didn't go to vote in great numbers . . . this suggests that they are not all convinced of the truth of this threat."