Salvadoran voters, ignoring rebel attempts to disrupt balloting, gave the rightist National Republican Alliance control of the National Assembly and turned President Jose Napoleon Duarte into a lame duck during his final year in office.

Duarte's ruling centrist Christian Democratic Party conceded defeat late Sunday, shortly after the rightist Alliance, known by its Spanish acronym ARENA, claimed victory for a majority of the seats in the 60-member assembly. Final official results were expected later Monday.In 1984 elections, Duarte's CDP won a clear majority of 33 seats in the National Assembly.

The ARENA victory means that Duarte will be a lame-duck president for the last year of his term and that his government will have difficulty getting its program through the National Assembly.

ARENA is led by cashiered Maj. Roberto D'Aubuisson, who had been accused of being behind the 1980 slaying of popular Archbishop of San Salvador Oscar Arnulfo Romero.

ARENA supporters danced in the streets of the capital late Sunday night, waving the red, white and blue banners of the party and setting off fireworks.

At Christian Democratic Party headquarters, where officials conceded the loss of the National Assembly to ARENA, as well as control of city hall in the capital of San Salvador, supporters wept.

Neither side said how many seats ARENA won in the National Assembly, and there were no official returns available by midnight.

ARENA has emphasized the country's severe economic crisis, government corruption scandals and the administration's inability to end the 8-year-old civil war, in which an estimated 70,000 people, mostly civilians, have died.

Sunday's elections also were seen as a portent of the 1989 presidential elections, in which Duarte is not eligible to run.

In the current assembly, the PDC holds 33 seats, compared with 13 for ARENA and 12 for the National Conciliation Party, or PCN. Small right-wing parties hold the two remaining seats.

The loss of the San Salvador mayorality was a bitter blow to the party, which has controlled city hall for the past 24 years and for which the Christian Democrats fielded Duarte's son, Alejandro Duarte, as their candidate.

"The Christian Democratic Party for the first time in history recognizes the victory of ARENA," CDP Vice President Rodolfo Castillo Claramount said.

"This is a democracy, and we accept the decision of the Salvadoran people," said Alejandro Duarte, who appeared shaken by the defeats.

ARENA candidate Armando Calderon Sol said he had defeated Alejandro Duarte to become mayor of the capital, which has been controlled by the Christian Democrats since 1964.

The election posed the toughest challenge by rightist political parties to the U.S.-backed Duarte since he came to power in 1984.

"We ask every Salvadoran to risk their lives for two minutes for democracy," Duarte said after he voted with his wife, Ines, at Parque Libertad in central San Salvador.