Uruguay's two main candidates were virtually tied after Sunday's general election - an unprecedented situation that has delayed an official result.
The tie is between two main candidates, leftist Daniel Martinez (Broad Front) and right-wing Luis Lacalle Pou (National Party), who was the favourite leader, according to opinion polls.
Uruguay's conservative opposition was on track to win the presidential election but an unexpected rise in votes for the Broad Front - a party that has governed the country for 15 years - led to a difference of just 28,000 votes, giving a narrow lead to the National Party.
With 99.4% of polling booths counted, Lacalle could become Uruguay's next president, with 48.7% of the vote ahead of Martinez, 47.48%.
But the conservative leader will need to wait to claim victory. The slim gap means that an official result could be delayed until Thursday or Friday.
Uruguay's electoral court has to count over 35,000 ballots cast by voters who could not make it to their assigned polling stations.
Lacalle said that he would also wait to claim victory and that the close result meant the two parties would need to work closely together in the period ahead.
"Formally we will know in a few days," he told supporters, adding that he believed the result was "irreversible".
As pre-election campaigns closed last week Lacalle had struck a confident tone, saying Uruguay was demanding change. Opinion polls showed him beating Martinez by a margin of 6-8 points.
Who is running?
The Broad Front, the ruling party for 15 years, has overseen a period of stability and growth: "the Uruguayan miracle". The country of 3.4 million people has experienced more than a decade of sustained economic growth, with an economy supported by farming and tourism. It also has the lowest index of inequality in South America.
Uruguay is known for its liberal progressive policies on legalised marijuana - in 2013 it became the first country in the modern era to legalise cannabis- and abortion rights, implemented during the mandate of former President José Mujica.
However, the ruling party has come under pressure recently from a slowing economy due to global trade woes and the effects of drought and flooding on the key farming sector.
Daniel Martinez - 62 years old - is the current leader of the left-wing coalition. He is an experienced politician and joined the Socialist Party at the early age of 16. Trained as an engineer, he became Minister of Industry and Energy in 2008 and mayor of Montevideo in 2015.
After knowing the results, Martinez warned about "fundamentalist" policies taking Uruguay sharply to the right.
Opposition leader Luis Lacalle Pou, who is 46, comes from a family of well-known politicians.
He is the son of former President Luis Alberto Lacalle (who governed from 1990 to 1995) and former Senator Julia Pou. Lacalle was a lawmaker between 2000 and 2015, and senator from 2015 until he presented his resignation to run in the general elections.
"It's the people... saying 'I want to shake up the government's drowsiness and change it,'" said Lacalle on Sunday, who became the front-runner after striking deals with a string of allies following an October first round.