Conservative candidate Alejandro Giammattei won Guatemala's presidential runoff on Sunday with a decisive lead over his rival, according to preliminary results from the Supreme Electoral Court (STE).

With 84 percent of the votes counted, Giammattei, of the Vamos (Let's Go for a Different Guatemala) party, garnered 59 percent of the ballots, or 1,650,976 votes.

Former first lady Sandra Torres, the candidate of the National Unity of Hope (UNE) party, trailed with 40 percent of the ballots, or 1,120,909 votes.

"Starting Jan. 14, we can't waste a single day. I want to tell you that tonight before going to sleep, we should ask God for his blessings and wisdom because we are going to have some tough times," Giammattei said in a victory speech shortly after the vote count showed he had a commanding lead.

Torres has won the first round on June 16 with 25 percent of the votes versus 14 percent for Giammattei, out of a crowded field of 19 presidential hopefuls.

However, going into the runoff, Giammattei, former director of the Guatemalan Penitentiary System, had a slight advantage as right-of-center voters consolidated behind him.