Guatemala City, Guatemala - US President Joe Biden congratulated Guatemala's new leader Bernardo Arevalo on Monday, lauding his counterpart's inauguration as "testament to our shared commitment to democracy and the will of the people."

"I look forward to continuing the strong partnership between our nations as we advance human rights, strengthen civilian security, combat corruption, address the root causes of migration, and expand economic opportunity for people across our hemisphere and around the world," Biden said in a White House statement.

Arevalo, a 65-year-old former lawmaker, diplomat, and sociologist, pulled off a major upset when he swept from obscurity to win elections last August, firing up voters in one of Latin America's poorest nations.

He took the oath of office after warding off a barrage of attempts to prevent him from taking power – including by prosecutors facing accusations of graft who are closely aligned with the country's political and economic ruling class.

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The US State Department also underlined the role of democracy in Guatemala after Arevalo's inauguration.

"We applaud the Guatemalan people for advancing the cause of democracy under challenging circumstances," Secretary of State Antony Blinken said in a statement.

Blinken commended "Guatemala's institutions, civil society, and the international community for safeguarding electoral integrity, voting systems, and processes."

Arevalo was inaugurated around midnight after hours of tug-of-war Sunday over the status of lawmakers in his party.

He takes over from Alejandro Giammattei, under whom several prosecutors fighting graft were arrested or forced into exile.

Guatemala is one of Latin America's most unequal countries, a reality that has, along with high rates of violent crime, compelled hundreds of thousands to risk the perilous migrant journey to the United States in hopes of a better life.

The United States has a history of intervention in Guatemala, with the CIA helping to overthrow the democratically-elected president in 1954. The US government continued to back Guatemalan military forces that killed more than 200,000 people, most of whom were Indigenous Mayans, during the country's bloody Civil War (1960-1996).