Efrain Alegre, the main opposition candidate in Paraguay's April 22 presidential election, signed a declaration on Wednesday in which he pledges to defend the "traditional" family, made up of a man and a woman, as well as to protect life from the moment of conception.

Alegre, leader of the Liberal Party, presented the document to journalists, which states that he will commit himself to "respect, protect, defend and promote the family made up of a man, a woman and their children, or any of their ascendants or descendants, as the foundation of society."

The document also says that the candidate pledges to defend "life from the moment of conception to the moment of natural death" and that, as president, he will "direct his administration on the basis of these principles."

Responding to journalists' questions, Alegre said that this is the same position he had when he ran in the 2013 presidential elections, when he lost to incumbent Horacio Cartes, of the Colorado Party.

"These are our positions and principles ... We have indicated before that marriage is between a man and a woman," Alegre said at his home in the Asuncion suburb of Lambare.

He added that these principles are established in the constitution and that he and his party have worked to defend them.

Alegre's pro-life position is similar to that of his main rival, Colorado Party standard-bearer Mario Abdo Benitez.

Alegre's Ganar coalition also includes the left-leaning Frente Guasu electoral alliance, which chose journalist Leonardo Rubin as the coalition's vice-presidential candidate.

Close to four million Paraguayans are set to vote in the April 22 elections.