RIO DE JANEIRO: After a stunning political comeback and massive victory party, Brazilian president-elect Luiz Inacio Lula da Silva faced a tough to-do list Monday - complicated by incumbent Jair Bolsonaro, who has not acknowledged defeat. Elected Sunday by the narrowest margin in Brazil's modern history -- 50.9 percent to 49.1 percent - charismatic but tarnished ex-president Lula will now return for an unprecedented third term at the helm of Latin America's biggest economy on Jan 1.

After a dirty, divisive campaign that left the country of 215 million people split in two, the 77-year-old leftist icon now faces a laundry list of challenges, including a struggling economy, rampant destruction of the Amazon rainforest, and an energized and angry far-right. But first, there is the giant question mark over whether Bolsonaro will accept defeat.

The far-right president has not spoken publicly or on his beloved social media accounts since the result was announced, raising fears over how he will react, after months of alleging fraud in the electoral system and a conspiracy against him. The transition period got off to a tense start as truckers and demonstrators blocked several highways across the country Monday in an apparent pro-Bolsonaro protest, burning tires and parking vehicles in the middle of the road to halt traffic.

Despite the rocky aftermath of the razor-thin runoff election, markets reacted favorably: after dipping slightly, stocks were up 1.2 percent in mid-morning trading in Sao Paulo, and the Brazilian real gained more than two percent against the dollar. "Lula remains likely to begin his term on a moderate note on economic policy, but risks over economic management will grow over time given a short honeymoon and a tough public opinion environment," the Eurasia Group consultancy said in a note. It downplayed the risk of a major power grab by Bolsonaro. "While the risk of near-term protests remains high, the risk of a serious institutional crisis remains very low," it said.

Lula, who vowed in his victory speech to restore Brazil's damaged image on the international stage, will meet Monday with Argentine President Alberto Fernandez in Sao Paulo, officials said. There was meanwhile radio silence from Bolsonaro. AFP journalists said the former army captain left his official residence without comment Monday morning for the presidential offices, where he was photographed walking down a corridor with a grim face.

There are fears Bolsonaro, 67, could attempt a Brazilian version of the Capitol riots that rocked the United States after his political role model, former US president Donald Trump, refused to accept his election defeat in 2020. But he may find himself isolated. Some key Bolsonaro allies have publicly recognized his loss, including the powerful speaker of the lower house of Congress, Arthur Lira.

And international leaders' congratulations for Lula poured in within hours, sometimes minutes. The leaders of the US, China, India, France, Britain, South Africa and numerous others sent Lula their congrats. US President Joe Biden reacted almost immediately, calling the elections "free, fair and credible". The European Union's leadership voiced hope the result would lead to ratification of a trade deal with South American bloc Mercosur, long stalled over concerns about rampant deforestation in the Amazon under Bolsonaro.

Norway announced it would resume paying nearly $500 million in aid for protecting the world's biggest rainforest, which it halted in 2019 over Bolsonaro's policies. "We had a head-on collision with Bolsonaro, whose approach was diametrically opposed (to Lula's) when it came to deforestation," Norwegian Environment Minister Espen Barth Eide told AFP.

Lula criticized his nemesis Sunday night for not acknowledging the result. "Anyplace else in the world, the defeated president would have called me to recognize his defeat," he said in his victory speech to a euphoric sea of red-clad supporters in Sao Paulo. The ex-metalworker vowed to work for "peace and unity" in the divided nation. "The Brazilian people don't want to fight anymore," he said. Easier said than done, according to political analysts. "It was a very narrow victory... (that left) half the population unhappy," said political scientist Leandro Consentino of Insper university in Sao Paulo. "Lula will have to show a lot of political skill to pacify the country." - AFP