BOGOTA, Aug. 7 (CGTN) -- Colombia's new president, Ivan Duque, took office on Tuesday and pledged to unite his South American nation, but insisted he would change a landmark peace accord with leftist rebels.

Duque, who is just 42 years old, wore a sash in the country's national colors on Tuesday. He took the oath of office in Bogota's Bolivar Square in the presence of several regional leaders including Mexico's Enrique Pena Nieto and Ecuador's Lenin Moreno.

In his inaugural address, he said he would take steps to fix "structural flaws" in the deal with the Revolutionary Armed Forces of Colombia (FARC), without offering concrete details.

Surrounded by friends and family, Duque also thanked voters for handing him the biggest electoral victory in Colombia’s history based on number of votes received. He struck a conciliatory tone, calling for the nation of more than 50 million people to unite behind him.

“With humility and honor, I tell the Colombian people that I will give all my energies to unite our country. No more divisions,” Duque told a crowd of cheering supporters in Bogota.

“I will not govern with hatred.”

Duque has also promised to bolster the 324 billion US dollar economy, keep investors happy by cutting business taxes, support the oil and coal sectors – top exports – and help increase domestic manufacturing.

Peace with rebels? Not so fast

Duque has long criticized the FARC deal as being too lenient as it allows former rebels who have been accused of atrocities to serve as lawmakers.

Ending 50 years of conflict, during which time over 260,000 people were killed and more than seven million were displaced, is no easy undertaking.

Meanwhile, Santos – who won a Nobel Peace Prize for his work on the FARC deal – admitted defeat in his bid to negotiate a ceasefire with the ELN, despite making "significant progress."

Duque made it clear that further progress would not come easy.

FARC leader Rodrigo Londono, also known as Timochenko, congratulated Duque on Twitter, calling for reconciliation and saying he respected Colombians’ decision.

As the hand-picked choice of Uribe, he enjoys considerable support from the powerful Democratic Center party his mentor launched.