Salvadoran archbishop Oscar Romero is set to be beatified Saturday, cementing his legacy among Catholics after decades of controversy over his defense of the poor and repressed, which divided both El Salvador and the Church.

Officials expect 285,000 faithful to attend the ceremony on San Salvador's main square, where Pope Francis's envoy for the occasion, Cardinal Angelo Amato, will confer the title of "blessed" on Romero, putting him one step from sainthood.

Four presidents, six cardinals and more than 100 bishops and archbishops are also expected to pay tribute to the man nicknamed the "Voice of the Voiceless," who was shot through the heart by a sniper on March 24, 1980 while delivering mass in a hospital chapel.

The assassination occurred at the outset of El Salvador's civil war, and propelled the country deeper into a brutal conflict that raged until 1992, when the right-wing government signed a peace deal with the leftist guerrillas of the Farabundo Marti National Liberation Front (FMLN).

No one was ever convicted of Romero's killing, but a UN-sponsored truth commission concluded it was carried out by a right-wing death squad under the orders of Roberto D'Aubuisson, a former army officer who died the year the war ended.

The movement to make Romero a saint was long resisted by conservative Catholics and the Salvadoran right, who saw veiled Marxism in his sermons eulogizing the poor and radio broadcasts condemning government repression.

The petition languished for years at the Vatican's Congregation for the Causes of Saints, finally moving forward in February when Pope Francis named Romero a martyr for the Church, one of the paths to sainthood.

The move signaled a shift at the Vatican under Francis, the first Latin American pope, whose call for a "poor Church, for the poor" is reminiscent of Romero's teachings.

Romero's murder had widespread impact in Latin America, a predominantly Roman Catholic region where several far-right regimes were then fighting leftist guerrillas.

Critics associated him with "liberation theology" -- a movement rooted in Latin America that advocates working with the poor to bring about social change -- though he did not actually adhere to the doctrine.

He remains divisive in El Salvador, though criticism is more muted than in the past.

Today, the former leftist guerrilla army, the FMLN, is governing the country.

Romero's tomb in the basement of San Salvador's cathedral now draws pilgrims from around the world, including President Barack Obama and UN Secretary General Ban Ki-moon.

El Salvador still faces deep poverty, and is torn by violence.

But the bloodshed is not caused by civil war, rather by the gangs whose ruthless battles to control the drug trade have given the country one of the world's highest murder rates.