Leftist economist Luis Arce assumed the Bolivian presidency on Sunday in a ceremony attended by foreign leaders, facing the challenge of uniting a deeply polarized society and reviving a virus-wracked economy.

Arce, who won election easily last month, was sworn in by newly invested vice president David Choquehuanca in the presence of parliamentarians, ordinary Bolivians and guests including King Felipe VI of Spain and the presidents of Argentina, Colombia and Paraguay.

His right hand raised, he pronounced the words "I swear."

"We are beginning a new stage in our history," he said later, "and we want to do so with a government that is for everyone, without discrimination of any kind. Our government will seek to rebuild our homeland in unity."

Colombian President Ivan Duque later met with Arce and said Bogota hoped to "continue strengthening trade, security and diplomatic relations" with La Paz within the framework of the Andean Community of nations, of which Colombia holds the rotating presidency.

The political rise of Arce, who served as economy minister to President Evo Morales, marks the return to power of the Movement for Socialism (MAS) after Morales renounced his office and fled the country in June 2019 amid widespread social protests.

As Morales's heir apparent, Arce scored a resounding first-round victory in the October 18 elections, outpolling his chief challenger, centrist Carlos Mesa, by 26 points.

Luis Arce (L) and Vice President David Choquehuanca greet one another at a swearing-in before parliamentarians and foreign dignitaries in La Paz on November 8, 2020
Luis Arce (L) and Vice President David Choquehuanca greet one another at a swearing-in before parliamentarians and foreign dignitaries in La Paz on November 8, 2020 ABI / JUAN JOSE PERALTA

Morales returned Monday from the border with Argentina, the country where he had sought refuge after first fleeing to Mexico.

He then headed to the central coca-growing region of El Chapare, where he has strong support among the rural population.

Analysts say Arce's biggest challenge may be to convincingly demonstrate that he really is in charge, and not simply being manipulated by the long dominant Morales.

He will have to do so while juggling numerous other difficulties.

Bolivia's politics are hugely polarized between east and west, cities and the countryside.

And there are accusations of resurging racism and courts that serve the government rather than justice.

Morales drew praise for presiding over Bolivia's "economic miracle" -- with Arce as his finance and economy minister -- but he was often lambasted for his authoritarian style.