Mexico's leftist and conservative candidates are both claiming victory in the presidential election, even though officials say the race is too close to call.
Luis Ugalde, head of the Federal Electoral Institute says the margin between the two main candidates is so close that all ballots will have to be counted before the outcome of the vote is clear. He says the counting will not be completed before Wednesday.
Despite the announced delay, leftist candidate Andres Manuel Lopez Obrador declared himself and his Party of the Democratic Revolution the election winners.
However, conservative Felipe Calderon of the National Action Party says he is leading in the ballot count.
Calderon served as energy minister under outgoing President Vicente Fox. If elected, he has promised to carry out broad economic and political reforms.
Lopez Obrador is the former mayor of Mexico City. He centered his campaign on promises to reduce poverty.
Mexican voters also cast ballots Sunday for members of congress and for governors in five states.
President Fox was barred from seeking re-election. This Mexican election was the first in which an estimated 10 million Mexicans living in the United States could cast ballots. Mexico's electoral institute says nearly 41 thousand of them registered to vote.